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.InputStreamReader;
import java.util.Scanner;

public class ProblemA {
    static long solve(long x, long y, long m) {
        long ans = 0;
        if (x>y) {long tmp = x; x = y; y = tmp;}
        if (x >= m || y >= m) return 0;
        if (x <= 0 && y <= 0) return -1;
        if (x < 0) {
            ans += (-x) / y;
            x += ans * y;
        }
        while (x < m && y < m) {
            long s = x + y;
            if (x<y) x = s; else y = s;
            ans++;
        }
        return ans;
    }

    static long solve2(long x, long y, long m) {
        for (int i=0; ; i++) {
            if (x > m || y > m) return i;
            long s = x + y;
            if (s <= x && s <= y) return -1;
            if (x<y) x = s; else y = s;
        }
    }
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(new InputStreamReader(System.in));
        long x = sc.nextLong(), y = sc.nextLong(), m = sc.nextLong();
        sc.close();
        System.out.println(solve(x, y, m));

        /*long best = -1;
        final int MAX = 100;
        for (int x=-MAX; x<=MAX; x++)
            for (int y=-MAX; y<=MAX; y++)
                for (int m=-MAX; m<=MAX; m++) {
                    long ans = solve(x, y, m);
                    if (ans>best) {
                        best = ans;
                        System.out.println(x+" "+y+" "+m+" "+ans);
                    }
                }*/

        //System.out.println(best);
        // solve(-100, 1, 90);
    }
}
