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.*;

public class A {

    static class Assert {
        static void check(boolean e) {
            if (!e) {
                throw new Error();
            }
        }
    }

    Scanner in;
    PrintWriter out;

    void solve() {
        long x = in.nextLong();
        long y = in.nextLong();
        long m = in.nextLong();
        if (x >= m || y >= m) {
            out.println(0);
            return;
        }
        if (x <= 0 && y <= 0) {
            out.println(-1);
            return;
        }
        Assert.check(m > 0);
        if (y <= 0) {
            long t = x;
            x = y;
            y = t;
        }
        Assert.check(y > 0);
        long count;
        if (x <= 0) {
            count = (-x + y - 1) / y;
            x += y * count;
        } else {
            count = 0;
        }
        Assert.check(x >= 0 && y > 0);
        while (x < m && y < m) {
            if (x > y) {
                y += x;
            } else {
                x += y;
            }
            count++;
        }
        out.println(count);
    }

    void run() {
        in = new Scanner(System.in);
        out = new PrintWriter(System.out);
        try {
            solve();
        } finally {
            out.close();
        }
    }

    public static void main(String args[]) {
        new A().run();
    }
}