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.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Scanner;
import java.util.StringTokenizer;
import java.util.TreeSet;

public class ProblemCC {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);

        long x = in.nextLong();
        long y = in.nextLong();

        long m = in.nextLong();

        long moves = 0;


        while (x < m && y < m) {
            long sum = x + y;

            if (x < y) {
                
                if (sum <= x) {
                    System.out.println("-1");
                    return;
                }
                
                if(sum >= y){
                    moves++;
                    x = sum;
                    continue;
                }
                
                long diff = y - x;
                
                diff /= Math.abs(y);
                
                sum = x + diff*y;
                moves += diff;
                
                x = sum;
            } else {
                if (sum <= y) {
                    System.out.println("-1");
                    return;
                }
                
                if(sum >= x){
                    moves++;
                    y = sum;
                    continue;
                    
                }
                long diff = x - y;
                diff /= Math.abs(x);
                sum = y + diff*x;
                moves += diff;
                y = sum;
            }
        }

        System.out.println(moves);
    }

}