Meka-Naruto plays a computer game. His character has the following ability: given an enemy hero, deal a instant damage to him, and then heal that enemy b health points at the end of every second, for exactly c seconds, starting one second after the ability is used. That means that if the ability is used at time t, the enemy's health decreases by a at time t, and then increases by b at time points t + 1, t + 2, ..., t + c due to this ability.

The ability has a cooldown of d seconds, i. e. if Meka-Naruto uses it at time moment t, next time he can use it is the time t + d. Please note that he can only use the ability at integer points in time, so all changes to the enemy's health also occur at integer times only.

The effects from different uses of the ability may stack with each other; that is, the enemy which is currently under k spells gets k⋅ b amount of heal this time. Also, if several health changes occur at the same moment, they are all counted at once.

Now Meka-Naruto wonders if he can kill the enemy by just using the ability each time he can (that is, every d seconds). The enemy is killed if their health points become 0 or less. Assume that the enemy's health is not affected in any way other than by Meka-Naruto's character ability. What is the maximal number of health points the enemy can have so that Meka-Naruto is able to kill them?

Input

The first line contains an integer t (1≤ t≤ 10^5) standing for the number of testcases.

Each test case is described with one line containing four numbers a, b, c and d (1≤ a, b, c, d≤ 10^6) denoting the amount of instant damage, the amount of heal per second, the number of heals and the ability cooldown, respectively.

Output

For each testcase in a separate line print -1 if the skill can kill an enemy hero with an arbitrary number of health points, otherwise print the maximal number of health points of the enemy that can be killed.

Example

Input


7
1 1 1 1
2 2 2 2
1 2 3 4
4 3 2 1
228 21 11 3
239 21 11 3
1000000 1 1000000 1


Output


1
2
1
5
534
-1
500000500000

Note

In the first test case of the example each unit of damage is cancelled in a second, so Meka-Naruto cannot deal more than 1 damage.

In the fourth test case of the example the enemy gets:

  * 4 damage (1-st spell cast) at time 0; 
  * 4 damage (2-nd spell cast) and 3 heal (1-st spell cast) at time 1 (the total of 5 damage to the initial health); 
  * 4 damage (3-nd spell cast) and 6 heal (1-st and 2-nd spell casts) at time 2 (the total of 3 damage to the initial health); 
  * and so on. 



One can prove that there is no time where the enemy gets the total of 6 damage or more, so the answer is 5. Please note how the health is recalculated: for example, 8-health enemy would not die at time 1, as if we first subtracted 4 damage from his health and then considered him dead, before adding 3 heal.

In the sixth test case an arbitrarily healthy enemy can be killed in a sufficient amount of time.

In the seventh test case the answer does not fit into a 32-bit integer type.
import java.io.*;
import java.util.*;

public class Solution {

    public static boolean useInFile = false;
    public static boolean useOutFile = false;

    public static void main(String args[]) throws IOException {
        InOut inout = new InOut();
        Resolver resolver = new Resolver(inout);
        resolver.solve();
        inout.flush();
    }

    private static class Resolver {

        final long LONG_INF = (long) 1e18;
        final int INF = (int) (1e9 + 7);
        final int MOD = 998244353;
        long f[], inv[];
        InOut inout;

        Resolver(InOut inout) {
            this.inout = inout;
        }

        void initF(int n, int mod) {
            f = new long[n + 1];
            f[1] = 1;
            for (int i = 2; i <= n; i++) {
                f[i] = (f[i - 1] * i) % mod;
            }
        }

        void initInv(int n, int mod) {
            inv = new long[n + 1];
            inv[n] = pow(f[n], mod - 2, mod);
            for (int i = inv.length - 2; i >= 0; i--) {
                inv[i] = inv[i + 1] * (i + 1) % mod;
            }
        }

        long cmn(int n, int m, int mod) {
            return f[n] * inv[m] % mod * inv[n - m] % mod;
        }

        int d[] = {0, -1, 0, 1, 0};

        boolean legal(int r, int c, int n, int m) {
            return r >= 0 && r < n && c >= 0 && c < m;
        }

        void dfs(int f, int p, int dst[], int cnt, int dp[], int low[]) {
            List<Integer> es = adj[f];
            dst[f] = cnt;
            low[f] = cnt;
            for (int i = 0; i < es.size(); i++) {
                int t = es.get(i);
                if (t == p) {
                    continue;
                }
                if (dst[t] == 0) {
                    dfs(t, f, dst, cnt + 1, dp, low);
                    if (low[t] >= dst[f]) {
                        dp[f]++;
                    }
                } else {
                    low[f] = Math.min(low[f], low[t]);
                }
            }
            if (es.size() == 1) {
                dp[f] = 1;
            } else if (es.size() > 1 && p != -1) {
                dp[f]++;
            }
        }

        void solve() throws IOException {
            int tt = 1;
            boolean hvt = true;
            if (hvt) {
                tt = nextInt();
//                tt = Integer.parseInt(nextLine());
            }
//            initF(2001, INF);
//            initInv(2001, INF);

            for (int cs = 1; cs <= tt; cs++) {
                long rs = 0;
//                int n = nextInt();
                long a = nextInt();
                long b = nextInt();
                long c = nextInt();
                long d = nextInt();
                if (a > b * c) {
                    rs = -1;
                } else if (d > c || a <= b * d) {
                    rs = a;
                } else {
                    rs = a;
                    long x = a;
                    long cnt = a / (b * d);
                    rs = Math.max(rs, a * (cnt + 1) - b * d * (1 + cnt) * cnt / 2);
                }




                format("%d", rs);
//                format("Case #%d: %d", cs, rs);

                if (cs < tt) {
                    format("\n");
//                    format(" ");
                }
//                flush();
            }

            int testtest = 0;
        }

        private void updateSegTree(int n, long l, SegmentTree lft) {
            long lazy;
            lazy = 1;
            for (int j = 1; j <= l; j++) {
                lazy = (lazy + cmn((int) l, j, INF)) % INF;
                lft.modify(1, j, j, lazy);
            }
            lft.modify(1, (int) (l + 1), n, lazy);
        }

        String next() throws IOException {
            return inout.next();
        }

        String next(int n) throws IOException {
            return inout.next(n);
        }

        String nextLine() throws IOException {
            return inout.nextLine();
        }

        int nextInt() throws IOException {
            return inout.nextInt();
        }

        long nextLong(int n) throws IOException {
            return inout.nextLong(n);
        }

        int[] anInt(int i, int j) throws IOException {
            int a[] = new int[j + 1];
            for (int k = i; k <= j; k++) {
                a[k] = nextInt();
            }
            return a;
        }

        long[] anLong(int i, int j, int len) throws IOException {
            long a[] = new long[j + 1];
            for (int k = i; k <= j; k++) {
                a[k] = nextLong(len);
            }
            return a;
        }

        void print(String s, boolean nextLine) {
            inout.print(s, nextLine);
        }

        void format(String format, Object... obj) {
            inout.format(format, obj);
        }

        void flush() {
            inout.flush();
        }

        void swap(long a[], int i, int j) {
            a[i] ^= a[j];
            a[j] ^= a[i];
            a[i] ^= a[j];
        }

        int getP(int x, int p[]) {
            if (p[x] == 0 || p[x] == x) {
                return x;
            }
            return p[x] = getP(p[x], p);
        }

        void union(int x, int y, int p[]) {
            if (x < y) {
                p[y] = x;
            } else {
                p[x] = y;
            }
        }

        boolean topSort() {
            int n = adj2.length - 1;
            int d[] = new int[n + 1];
            for (int i = 1; i <= n; i++) {
                for (int j = 0; j < adj2[i].size(); j++) {
                    d[adj2[i].get(j)[0]]++;
                }
            }
            List<Integer> list = new ArrayList<>();
            for (int i = 1; i <= n; i++) {
                if (d[i] == 0) {
                    list.add(i);
                }
            }
            for (int i = 0; i < list.size(); i++) {
                for (int j = 0; j < adj2[list.get(i)].size(); j++) {
                    int t = adj2[list.get(i)].get(j)[0];
                    d[t]--;
                    if (d[t] == 0) {
                        list.add(t);
                    }
                }
            }
            return list.size() == n;
        }

        class SegmentTreeNode {
            long defaultVal = 0;
            int l, r;
            long val = defaultVal, lazy = defaultVal;

            SegmentTreeNode(int l, int r) {
                this.l = l;
                this.r = r;
            }
        }

        class SegmentTree {
            SegmentTreeNode tree[];
            long inf = Long.MIN_VALUE;
            long c[];

            SegmentTree(int n) {
                assert n > 0;
                tree = new SegmentTreeNode[n * 3 + 1];
            }

            void setAn(long cn[]) {
                c = cn;
            }

            SegmentTree build(int k, int l, int r) {
                if (l > r) {
                    return this;
                }
                if (null == tree[k]) {
                    tree[k] = new SegmentTreeNode(l, r);
                }
                if (l == r) {
                    return this;
                }
                int mid = (l + r) >> 1;
                build(k << 1, l, mid);
                build(k << 1 | 1, mid + 1, r);
                return this;
            }

            void pushDown(int k) {
                if (tree[k].l == tree[k].r) {
                    return;
                }
                long lazy = tree[k].lazy;
                tree[k << 1].val = ((c[tree[k << 1].l] - c[tree[k << 1].r + 1] + MOD) % MOD * lazy) % MOD;
                tree[k << 1].lazy = lazy;
                tree[k << 1 | 1].val = ((c[tree[k << 1 | 1].l] - c[tree[k << 1 | 1].r + 1] + MOD) % MOD * lazy) % MOD;
                tree[k << 1 | 1].lazy = lazy;
                tree[k].lazy = 0;
            }

            void modify(int k, int l, int r, long val) {
                if (tree[k].l >= l && tree[k].r <= r) {
                    tree[k].val = ((c[tree[k].l] - c[tree[k].r + 1] + MOD) % MOD * val) % MOD;
                    tree[k].lazy = val;
                    return;
                }
                int mid = (tree[k].l + tree[k].r) >> 1;
                if (tree[k].lazy != 0) {
                    pushDown(k);
                }
                if (mid >= l) {
                    modify(k << 1, l, r, val);
                }
                if (mid + 1 <= r) {
                    modify(k << 1 | 1, l, r, val);
                }
                tree[k].val = (tree[k << 1].val + tree[k << 1 | 1].val) % MOD;
            }

            long query(int k, int l, int r) {
                if (tree[k].l > r || tree[k].r < l) {
                    return 0;
                }
                if (tree[k].lazy != 0) {
                    pushDown(k);
                }
                if (tree[k].l >= l && tree[k].r <= r) {
                    return tree[k].val;
                }
                long ans = (query(k << 1, l, r) + query(k << 1 | 1, l, r)) % MOD;
                if (tree[k].l < tree[k].r) {
                    tree[k].val = (tree[k << 1].val + tree[k << 1 | 1].val) % MOD;
                }
                return ans;
            }
        }


        class BinaryIndexedTree {

            int n = 1;
            long C[];

            BinaryIndexedTree(int sz) {
                while (n <= sz) {
                    n <<= 1;
                }
                n = sz + 1;
                C = new long[n];
            }

            int lowbit(int x) {
                return x & -x;
            }

            void add(int x, long val) {
                while (x < n) {
                    C[x] += val;
                    x += lowbit(x);
                }
            }

            long getSum(int x) {
                long res = 0;
                while (x > 0) {
                    res += C[x];
                    x -= lowbit(x);
                }
                return res;
            }

            int binSearch(long sum) {
                if (sum == 0) {
                    return 0;
                }
                int n = C.length;
                int mx = 1;
                while (mx < n) {
                    mx <<= 1;
                }
                int res = 0;
                for (int i = mx / 2; i >= 1; i >>= 1) {
                    if (C[res + i] < sum) {
                        sum -= C[res + i];
                        res += i;
                    }
                }
                return res + 1;
            }
        }

        int mnS;
        int mxS;
        Map<Integer, TrieNode> SS = new HashMap<>();

        class TrieNode {
            int cnt = 0;
            boolean isMin = false;
            boolean isMax = false;
            int mnIdx = 26;
            int mxIdx = -1;

            TrieNode next[];

            TrieNode() {
                next = new TrieNode[26];
            }

            private void insert(TrieNode trie, char ch[], int i, int j) {
                while (i < ch.length) {
                    int idx = ch[i] - 'a';
                    if (null == trie.next[idx]) {
                        trie.next[idx] = new TrieNode();
                    }
                    trie.cnt++;
                    int lastMnIdx = trie.mnIdx;
                    int lastMxIdx = trie.mxIdx;
                    trie.mnIdx = Math.min(trie.mnIdx, idx);
                    trie.mxIdx = Math.max(trie.mxIdx, idx);
                    if (trie.isMin && lastMnIdx != trie.mnIdx) {
                        if (lastMnIdx != 26) {
                            notMin(trie.next[lastMnIdx]);
                        }
                        trie.next[trie.mnIdx].isMin = true;
                    }
                    if (trie.isMax && lastMxIdx != trie.mxIdx) {
                        if (lastMxIdx >= 0) {
                            notMax(trie.next[lastMxIdx]);
                        }
                        trie.next[trie.mxIdx].isMax = true;
                    }
                    trie = trie.next[idx];
                    i++;
                }
                SS.put(j + 1, trie);
                if (trie.cnt == 0) {
                    if (trie.isMin) {
                        mnS = j + 1;
                    }
                    if (trie.isMax) {
                        mxS = j + 1;
                    }
                }
            }

            private void notMin(TrieNode trie) {
                while (null != trie) {
                    trie.isMin = false;
                    int val = trie.mnIdx;
                    if (val >= 26 || val < 0 || null == trie.next[val]) {
                        break;
                    }
                    trie = trie.next[val];
                }
            }

            private void notMax(TrieNode trie) {
                while (null != trie) {
                    trie.isMax = false;
                    int val = trie.mxIdx;
                    if (val >= 26 || val < 0 || null == trie.next[val]) {
                        break;
                    }
                    trie = trie.next[val];
                }
            }
        }

        //Binary tree
        class TreeNode {
            int val;
            int tier = -1;
            TreeNode parent;
            TreeNode left;
            TreeNode right;

            TreeNode(int val) {
                this.val = val;
            }
        }

        //binary tree dfs
        void tierTree(TreeNode root) {
            if (null == root) {
                return;
            }
            if (null != root.parent) {
                root.tier = root.parent.tier + 1;
            } else {
                root.tier = 0;
            }
            tierTree(root.left);
            tierTree(root.right);
        }

        //LCA start
        TreeNode[][] lca;
        TreeNode[] tree;

        void lcaDfsTree(TreeNode root) {
            if (null == root) {
                return;
            }
            tree[root.val] = root;
            TreeNode nxt = root.parent;
            int idx = 0;
            while (null != nxt) {
                lca[root.val][idx] = nxt;
                nxt = lca[nxt.val][idx];
                idx++;
            }
            lcaDfsTree(root.left);
            lcaDfsTree(root.right);
        }

        TreeNode lcaTree(TreeNode root, int n, TreeNode x, TreeNode y) throws IOException {
            if (null == root) {
                return null;
            }
            if (-1 == root.tier) {
                tree = new TreeNode[n + 1];
                tierTree(root);
            }
            if (null == lca) {
                lca = new TreeNode[n + 1][31];
                lcaDfsTree(root);
            }
            int z = Math.abs(x.tier - y.tier);
            int xx = x.tier > y.tier ? x.val : y.val;
            while (z > 0) {
                final int zz = z;
                int l = (int) BinSearch.bs(0, 31
                        , k -> zz < (1 << k));
                xx = lca[xx][l].val;
                z -= 1 << l;
            }
            int yy = y.val;
            if (x.tier <= y.tier) {
                yy = x.val;
            }
            while (xx != yy) {
                final int xxx = xx;
                final int yyy = yy;
                int l = (int) BinSearch.bs(0, 31
                        , k -> (1 << k) <= tree[xxx].tier && lca[xxx][(int) k] != lca[yyy][(int) k]);
                xx = lca[xx][l].val;
                yy = lca[yy][l].val;
            }
            return tree[xx];
        }
        //LCA end

        //graph
        List<Integer> adj[];
        List<int[]> adj2[];

        void initGraph(int n, int m, boolean hasW, boolean directed, int type) throws IOException {
            if (type == 1) {
                adj = new List[n + 1];
            } else {
                adj2 = new List[n + 1];
            }
            for (int i = 1; i <= n; i++) {
                if (type == 1) {
                    adj[i] = new ArrayList<>();
                } else {
                    adj2[i] = new ArrayList<>();
                }
            }
            for (int i = 0; i < m; i++) {
                int f = nextInt();
                int t = nextInt();
                if (type == 1) {
                    adj[f].add(t);
                    if (!directed) {
                        adj[t].add(f);
                    }
                } else {
                    int w = hasW ? nextInt() : 0;
                    adj2[f].add(new int[]{t, w});
                    if (!directed) {
                        adj2[t].add(new int[]{f, w});
                    }
                }
            }
        }

        void getDiv(Map<Integer, Integer> map, long n) {
            int sqrt = (int) Math.sqrt(n);
            for (int i = 2; i <= sqrt; i++) {
                int cnt = 0;
                while (n % i == 0) {
                    cnt++;
                    n /= i;
                }
                if (cnt > 0) {
                    map.put(i, cnt);
                }
            }
            if (n > 1) {
                map.put((int) n, 1);
            }
        }

        boolean[] generatePrime(int n) {
            boolean p[] = new boolean[n + 1];
            p[2] = true;

            for (int i = 3; i <= n; i += 2) {
                p[i] = true;
            }

            for (int i = 3; i <= Math.sqrt(n); i += 2) {
                if (!p[i]) {
                    continue;
                }
                for (int j = i * i; j <= n; j += i << 1) {
                    p[j] = false;
                }
            }
            return p;
        }

        boolean isPrime(long n) { //determines if n is a prime number
            int p[] = {2, 3, 5, 233, 331};
            int pn = p.length;
            long s = 0, t = n - 1;//n - 1 = 2^s * t
            while ((t & 1) == 0) {
                t >>= 1;
                ++s;
            }
            for (int i = 0; i < pn; ++i) {
                if (n == p[i]) {
                    return true;
                }
                long pt = pow(p[i], t, n);
                for (int j = 0; j < s; ++j) {
                    long cur = llMod(pt, pt, n);
                    if (cur == 1 && pt != 1 && pt != n - 1) {
                        return false;
                    }
                    pt = cur;
                }
                if (pt != 1) {
                    return false;
                }
            }
            return true;
        }

        long[] llAdd2(long a[], long b[], long mod) {
            long c[] = new long[2];
            c[1] = (a[1] + b[1]) % (mod * mod);
            c[0] = (a[1] + b[1]) / (mod * mod) + a[0] + b[0];
            return c;
        }

        long[] llMod2(long a, long b, long mod) {
            long x1 = a / mod;
            long y1 = a % mod;
            long x2 = b / mod;
            long y2 = b % mod;
            long c = (x1 * y2 + x2 * y1) / mod;
            c += x1 * x2;
            long d = (x1 * y2 + x2 * y1) % mod * mod + y1 * y2;
            return new long[]{c, d};
        }

        long llMod(long a, long b, long mod) {
            if (a > mod || b > mod) {
                return (a * b - (long) ((double) a / mod * b + 0.5) * mod + mod) % mod;
            }
            return a * b % mod;
//        long r = 0;
//        a %= mod;
//        b %= mod;
//        while (b > 0) {
//            if ((b & 1) == 1) {
//                r = (r + a) % mod;
//            }
//            b >>= 1;
//            a = (a << 1) % mod;
//        }
//        return r;
        }

        long pow(long a, long n) {
            long ans = 1;
            while (n > 0) {
                if ((n & 1) == 1) {
                    ans = ans * a;
                }
                a = a * a;
                n >>= 1;
            }
            return ans;
        }

        long pow(long a, long n, long mod) {
            long ans = 1;
            while (n > 0) {
                if ((n & 1) == 1) {
                    ans = llMod(ans, a, mod);
                }
                a = llMod(a, a, mod);
                n >>= 1;
            }
            return ans;
        }

        private long[][] initC(int n) {
            long c[][] = new long[n][n];

            for (int i = 0; i < n; i++) {
                c[i][0] = 1;
            }

            for (int i = 1; i < n; i++) {
                for (int j = 1; j <= i; j++) {
                    c[i][j] = c[i - 1][j - 1] + c[i - 1][j];
                }
            }
            return c;
        }

        /**
         * ps: n >= m, choose m from n;
         */
//        private int cmn(long n, long m) {
//            if (m > n) {
//                n ^= m;
//                m ^= n;
//                n ^= m;
//            }
//            m = Math.min(m, n - m);
//
//            long top = 1;
//            long bot = 1;
//            for (long i = n - m + 1; i <= n; i++) {
//                top = (top * i) % MOD;
//            }
//            for (int i = 1; i <= m; i++) {
//                bot = (bot * i) % MOD;
//            }
//
//            return (int) ((top * pow(bot, MOD - 2, MOD)) % MOD);
//        }

        long[] exGcd(long a, long b) {
            if (b == 0) {
                return new long[]{a, 1, 0};
            }
            long[] ans = exGcd(b, a % b);
            long x = ans[2];
            long y = ans[1] - a / b * ans[2];
            ans[1] = x;
            ans[2] = y;
            return ans;
        }

        long gcd(long a, long b) {
            if (a < b) {
                return gcd(b, a);
            }
            while (b != 0) {
                long tmp = a % b;
                a = b;
                b = tmp;
            }
            return a;
        }

        int[] unique(int a[], Map<Integer, Integer> idx) {
            int tmp[] = a.clone();
            Arrays.sort(tmp);
            int j = 0;
            for (int i = 0; i < tmp.length; i++) {
                if (i == 0 || tmp[i] > tmp[i - 1]) {
                    idx.put(tmp[i], j++);
                }
            }
            int rs[] = new int[j];
            j = 0;
            for (int key : idx.keySet()) {
                rs[j++] = key;
            }
            Arrays.sort(rs);
            return rs;
        }

        boolean isEven(long n) {
            return (n & 1) == 0;
        }

        static class BinSearch {

            static long bs(long l, long r, IBinSearch sort) throws IOException {
                while (l < r) {
                    long m = l + (r - l) / 2;
                    if (sort.binSearchCmp(m)) {
                        l = m + 1;
                    } else {
                        r = m;
                    }
                }
                return l;
            }

            interface IBinSearch {
                boolean binSearchCmp(long k) throws IOException;
            }

        }
    }

    private static class InOut {
        private BufferedReader br;
        private StreamTokenizer st;
        private PrintWriter pw;

        InOut() throws FileNotFoundException {
            if (useInFile) {
                System.setIn(new FileInputStream("resources/inout/in.text"));
            }
            if (useOutFile) {
                System.setOut(new PrintStream("resources/inout/out.text"));
            }
            br = new BufferedReader(new InputStreamReader(System.in));
            st = new StreamTokenizer(br);
            pw = new PrintWriter(new OutputStreamWriter(System.out));
            st.ordinaryChar('\'');
            st.ordinaryChar('\"');
            st.ordinaryChar('/');
        }

        private long[] anLong(int n) throws IOException {
            long a[] = new long[n];
            for (int i = 0; i < n; i++) {
                a[i] = nextInt();
            }
            return a;
        }

        private String next() throws IOException {
            st.nextToken();
            return st.sval;
        }

        private String next(int len) throws IOException {
            char ch[] = new char[len];
            int cur = 0;
            char c;
            while ((c = (char) br.read()) == '\n' || c == '\r' || c == ' ' || c == '\t') ;
            do {
                ch[cur++] = c;
            } while (!((c = (char) br.read()) == '\n' || c == '\r' || c == ' ' || c == '\t'));
            return String.valueOf(ch, 0, cur);
        }

        private int nextInt() throws IOException {
            st.nextToken();
            return (int) st.nval;
        }

        private long nextLong(int n) throws IOException {
            return Long.parseLong(next(n));
        }

        private double nextDouble() throws IOException {
            st.nextToken();
            return st.nval;
        }

        private String[] nextSS(String reg) throws IOException {
            return br.readLine().split(reg);
        }

        private String nextLine() throws IOException {
            return br.readLine();
        }

        private void print(String s, boolean newLine) {
            if (null != s) {
                pw.print(s);
            }
            if (newLine) {
                pw.println();
            }
        }

        private void format(String format, Object... obj) {
            pw.format(format, obj);
        }

        private void flush() {
            pw.flush();
        }
    }

    private static class FFT {
        double[] roots;
        int maxN;

        public FFT(int maxN) {
            this.maxN = maxN;
            initRoots();
        }

        public long[] multiply(int[] a, int[] b) {
            int minSize = a.length + b.length - 1;
            int bits = 1;
            while (1 << bits < minSize) bits++;
            int N = 1 << bits;
            double[] aa = toComplex(a, N);
            double[] bb = toComplex(b, N);
            fftIterative(aa, false);
            fftIterative(bb, false);
            double[] c = new double[aa.length];
            for (int i = 0; i < N; i++) {
                c[2 * i] = aa[2 * i] * bb[2 * i] - aa[2 * i + 1] * bb[2 * i + 1];
                c[2 * i + 1] = aa[2 * i] * bb[2 * i + 1] + aa[2 * i + 1] * bb[2 * i];
            }
            fftIterative(c, true);
            long[] ret = new long[minSize];
            for (int i = 0; i < ret.length; i++) {
                ret[i] = Math.round(c[2 * i]);
            }
            return ret;
        }

        static double[] toComplex(int[] arr, int size) {
            double[] ret = new double[size * 2];
            for (int i = 0; i < arr.length; i++) {
                ret[2 * i] = arr[i];
            }
            return ret;
        }

        void initRoots() {
            roots = new double[2 * (maxN + 1)];
            double ang = 2 * Math.PI / maxN;
            for (int i = 0; i <= maxN; i++) {
                roots[2 * i] = Math.cos(i * ang);
                roots[2 * i + 1] = Math.sin(i * ang);
            }
        }

        int bits(int N) {
            int ret = 0;
            while (1 << ret < N) ret++;
            if (1 << ret != N) throw new RuntimeException();
            return ret;
        }

        void fftIterative(double[] array, boolean inv) {
            int bits = bits(array.length / 2);
            int N = 1 << bits;
            for (int from = 0; from < N; from++) {
                int to = Integer.reverse(from) >>> (32 - bits);
                if (from < to) {
                    double tmpR = array[2 * from];
                    double tmpI = array[2 * from + 1];
                    array[2 * from] = array[2 * to];
                    array[2 * from + 1] = array[2 * to + 1];
                    array[2 * to] = tmpR;
                    array[2 * to + 1] = tmpI;
                }
            }
            for (int n = 2; n <= N; n *= 2) {
                int delta = 2 * maxN / n;
                for (int from = 0; from < N; from += n) {
                    int rootIdx = inv ? 2 * maxN : 0;
                    double tmpR, tmpI;
                    for (int arrIdx = 2 * from; arrIdx < 2 * from + n; arrIdx += 2) {
                        tmpR = array[arrIdx + n] * roots[rootIdx] - array[arrIdx + n + 1] * roots[rootIdx + 1];
                        tmpI = array[arrIdx + n] * roots[rootIdx + 1] + array[arrIdx + n + 1] * roots[rootIdx];
                        array[arrIdx + n] = array[arrIdx] - tmpR;
                        array[arrIdx + n + 1] = array[arrIdx + 1] - tmpI;
                        array[arrIdx] += tmpR;
                        array[arrIdx + 1] += tmpI;
                        rootIdx += (inv ? -delta : delta);
                    }
                }
            }
            if (inv) {
                for (int i = 0; i < array.length; i++) {
                    array[i] /= N;
                }
            }
        }
    }
}
