Let us call a pair of integer numbers m-perfect, if at least one number in the pair is greater than or equal to m. Thus, the pairs (3, 3) and (0, 2) are 2-perfect while the pair (-1, 1) is not.

Two integers x, y are written on the blackboard. It is allowed to erase one of them and replace it with the sum of the numbers, (x + y).

What is the minimum number of such operations one has to perform in order to make the given pair of integers m-perfect?

Input

Single line of the input contains three integers x, y and m ( - 1018 ≤ x, y, m ≤ 1018).

Please, do not use the %lld specifier to read or write 64-bit integers in C++. It is preffered to use the cin, cout streams or the %I64d specifier.

Output

Print the minimum number of operations or "-1" (without quotes), if it is impossible to transform the given pair to the m-perfect one.

Examples

Input

1 2 5


Output

2


Input

-1 4 15


Output

4


Input

0 -1 5


Output

-1

Note

In the first sample the following sequence of operations is suitable: (1, 2) <image> (3, 2) <image> (5, 2).

In the second sample: (-1, 4) <image> (3, 4) <image> (7, 4) <image> (11, 4) <image> (15, 4).

Finally, in the third sample x, y cannot be made positive, hence there is no proper sequence of operations.
import java.io.*;
import java.util.*;

import static java.lang.Math.*;

public class Main extends PrintWriter {
    BufferedReader in;
    StringTokenizer stok;
    final Random rand = new Random(31);
    final int inf = (int) 1e9;
    final long linf = (long) 1e18;

    final static String IO = "_std";

    void solve() throws IOException {
        long x = nextLong();
        long y = nextLong();
        long m = nextLong();
        if (x >= m || y >= m) {
            println(0);
            return;
        }
        if (x <= 0 && y <= 0) {
            println(-1);
            return;
        }
        if (x > y) {
            long _ = x;
            x = y;
            y = _;
        }
        long s1 = 0;
        if (x <= 0) {
            s1 = (-x) / y + 1;
            x += s1 * y;
        }
        long ans = Long.MAX_VALUE;
        while (x < m && y < m) {
            if (x > y) {
                long _ = x;
                x = y;
                y = _;
            }
            ans = min(ans, s1 + (m - y + x - 1) / x);
            x += y;
            s1++;
        }
        println(min(ans, s1));
    }

    Main() {
        super(System.out);
        in = new BufferedReader(new InputStreamReader(System.in));
    }

    Main(String fileIn, String fileOut) throws IOException {
        super(fileOut);
        in = new BufferedReader(new FileReader(fileIn));
    }

    public static void main(String[] args) throws IOException {
        Main main;
        if ("_std".equals(IO)) {
            main = new Main();
        } else if ("_iodef".equals(IO)) {
            main = new Main("input.txt", "output.txt");
        } else {
            main = new Main(IO + ".in", IO + ".out");
        }
        main.solve();
        main.close();
    }

    String next() throws IOException {
        while (stok == null || !stok.hasMoreTokens()) {
            String s = in.readLine();
            if (s == null) {
                return null;
            }
            stok = new StringTokenizer(s);
        }
        return stok.nextToken();
    }

    int nextInt() throws IOException {
        return Integer.parseInt(next());
    }

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

    double nextDouble() throws IOException {
        return Double.parseDouble(next());
    }

    int[] nextIntArray(int len) throws IOException {
        int[] a = new int[len];
        for (int i = 0; i < len; i++) {
            a[i] = nextInt();
        }
        return a;
    }

    int[] nextIntArraySorted(int len) throws IOException {
        int[] a = nextIntArray(len);
        shuffle(a);
        Arrays.sort(a);
        return a;
    }

    void shuffle(int[] a) {
        for (int i = 1; i < a.length; i++) {
            int x = rand.nextInt(i + 1);
            int _ = a[i];
            a[i] = a[x];
            a[x] = _;
        }
    }

    boolean nextPermutation(int[] p) {
        for (int a = p.length - 2; a >= 0; --a) {
            if (p[a] < p[a + 1])
                for (int b = p.length - 1; ; --b)
                    if (p[b] > p[a]) {
                        int t = p[a];
                        p[a] = p[b];
                        p[b] = t;
                        for (++a, b = p.length - 1; a < b; ++a, --b) {
                            t = p[a];
                            p[a] = p[b];
                            p[b] = t;
                        }
                        return true;
                    }
        }
        return false;
    }

    <T> List<T>[] createAdjacencyList(int n) {
        List<T>[] res = new List[n];
        for (int i = 0; i < n; i++) {
            res[i] = new ArrayList<>();
        }
        return res;
    }
}