You are given n integers a1, a2, ..., an. Find the number of pairs of indexes i, j (i < j) that ai + aj is a power of 2 (i. e. some integer x exists so that ai + aj = 2x).

Input

The first line contains the single positive integer n (1 ≤ n ≤ 105) — the number of integers.

The second line contains n positive integers a1, a2, ..., an (1 ≤ ai ≤ 109).

Output

Print the number of pairs of indexes i, j (i < j) that ai + aj is a power of 2.

Examples

Input

4
7 3 2 1


Output

2


Input

3
1 1 1


Output

3

Note

In the first example the following pairs of indexes include in answer: (1, 4) and (2, 4).

In the second example all pairs of indexes (i, j) (where i < j) include in answer.
import java.util.*;
import java.io.*;
import java.math.BigInteger;
import java.text.*;
public class Main {
    static long mod = 1000_000_007;
    static long mod1 = 998244353;
    static boolean fileIO = false;
    static boolean memory = true;
    static FastScanner f;
    static PrintWriter pw;
    static double eps = (double)1e-6;
    static FileWriter fw;
    static long oo = Long.MAX_VALUE;
 
    // N = 1 or N = max ?
    // longs vs. ints ?
    // max / min ?

    static int n , arr[];

    public static void solve() throws Exception {
        n = f.ni();
        arr = new int[n];

        HashMap<Integer , Integer> mp = new HashMap<>();

        for (int i = 0; i < n; ++i) {
            arr[i] = f.ni();
            if (mp.get(arr[i]) != null) mp.put(arr[i] , mp.get(arr[i]) + 1);
            else mp.put(arr[i] , 1);
        }

        sort(arr);

        long ans = 0;
        for (int i = 0; i < n; ++i) {
            mp.put(arr[i] , mp.get(arr[i]) - 1);
            if (mp.get(arr[i]) == 0) mp.remove(arr[i]);
            long make = 1;
            while (make <= 2e9) {
                ans += mp.getOrDefault((int)make - arr[i] , 0);
                make *= 2;
            }
        }

        pn(ans);
    }      
 
    public static void main(String[] args)throws Exception {
        if(memory) new Thread(null, new Runnable() {public void run(){try{new Main().run();}catch(Exception e){e.printStackTrace();System.exit(1);}}}, "", 1 << 28).start();
        else new Main().run();
    }
        
/******************************END OF MAIN PROGRAM*******************************************/
    void run()throws Exception {
        if (System.getProperty("ONLINE_JUDGE") == null) {
            f = new FastScanner("");
            pw = new PrintWriter(System.out);
            fw = new FileWriter("!out.txt");
        }
        else {
            f = new FastScanner();
            pw = new PrintWriter(System.out);
            fw = new FileWriter("!out.txt");
        }
        //
        int t = 1;
        int tt = 1;

        while(t --> 0) {
            //p("Case #" + (tt++) + ": ");
            //fw.write("\n");
            solve();
        }
        
        pw.flush(); 
        pw.close(); 
    }
 
    public static class FastScanner {
        BufferedReader br;
        StringTokenizer st;
 
        public FastScanner(String str) throws Exception {
            try {
                br = new BufferedReader(new FileReader("!a.txt"));
            }
            catch (Exception e) {
                e.printStackTrace();
            }
        }
 
        public FastScanner() {
            br = new BufferedReader(new InputStreamReader(System.in));
        }
 
        public String next()throws IOException {
            while (st == null || !st.hasMoreTokens())
                st = new StringTokenizer(br.readLine());
            return st.nextToken();
        }
 
        public int ni() throws IOException {return Integer.parseInt(next());}
 
        public long nl() throws IOException {return Long.parseLong(next());}
 
        public String nextLine() throws IOException {return br.readLine();}
 
        public double nd() throws IOException {return Double.parseDouble(next());}
 
    }
 
    public static void pn(Object... o) {for(int i = 0; i < o.length; ++i) pw.print(o[i] + (i + 1 < o.length ? " ": "\n"));}
    public static void p(Object... o) {for(int i = 0; i < o.length; ++i) pw.print(o[i] + (i + 1 < o.length ? " " : ""));}
    public static void pni(Object... o) {for(Object obj : o) pw.print(obj + " "); pw.println(); pw.flush();}
    public static int gcd(int a,int b){if(b==0)return a;else{return gcd(b,a%b);}}
    public static long gcd(long a,long b){if(b==0l)return a;else{return gcd(b,a%b);}}
    public static long lcm(long a,long b){return (a*b/gcd(a,b));}
    public static long pow(long a,long b){long res=1;while(b>0){if((b&1)==1)res=res*a;b>>=1;a=a*a;}return res;}
    public static int pow(int a,int b){int res=1;while(b>0){if((b&1)==1)res=res*a;b>>=1;a=a*a;}return res;}
    public static long mpow(long a,long b, long m){long res=1;while(b>0){if((b&1)==1)res=((res%m)*(a%m))%m;b>>=1;a=((a%m)*(a%m))%m;}return res;}
    public static long mul(long a , long b , long mod){return ((a%mod)*(b%mod)%mod);}
    public static long adp(long a , long b){return ((a%mod)+(b%mod)%mod);}
    public static int dig(long a){int cnt=0;while(a>0){a/=10;++cnt;}return Math.max(1,cnt);}
    public static int dig(int a){int cnt=0;while(a>0){a/=10;++cnt;}return Math.max(1,cnt);}
    public static boolean isPrime(long n){if(n<=1)return false;if(n<=3)return true;if(n%2==0||n%3==0)return false;for(long i=5;i*i<=n;i=i+6)if(n%i==0||n%(i+2)==0)return false;return true;}
    public static boolean isPrime(int n){if(n<=1)return false;if(n<=3)return true;if(n%2==0||n%3==0)return false;for(int i=5;i*i<=n;i=i+6)if(n%i==0||n%(i+2)==0)return false;return true;}
    public static HashSet<Long> factors(long n){HashSet<Long> hs=new HashSet<Long>();for(long i=1;i<=(long)Math.sqrt(n);i++){if(n%i==0){hs.add(i);hs.add(n/i);}}return hs;}
    public static HashSet<Integer> factors(int n){HashSet<Integer> hs=new HashSet<Integer>();for(int i=1;i<=(int)Math.sqrt(n);i++){if(n%i==0){hs.add(i);hs.add(n/i);}}return hs;}
    public static HashSet<Long> pf(long n){HashSet<Long> ff=factors(n);HashSet<Long> ans=new HashSet<Long>();for(Long i:ff)if(isPrime(i))ans.add(i);return ans;}
    public static HashSet<Integer> pf(int n){HashSet<Integer> ff=factors(n);HashSet<Integer> ans=new HashSet<Integer>();for(Integer i:ff)if(isPrime(i))ans.add(i);return ans;}
    public static int gnv(char c){return Character.getNumericValue(c);}
    public static void sort(int[] a){ArrayList<Integer> l=new ArrayList<>();for(int i:a)l.add(i);Collections.sort(l);for(int i=0;i<a.length;++i)a[i]=l.get(i);}
    public static void sort(long[] a){ArrayList<Long> l=new ArrayList<>();for(long i:a)l.add(i);Collections.sort(l);for(int i=0;i<a.length;++i)a[i]=l.get(i);}
    public static void sort(ArrayList<Integer> a){Collections.sort(a);}
}