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.
/*
 *Author : Daipayan Mukherjee (Admin)
 *Created On: 3/1/2020,Sunday at 1:25 PM
 */
 
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
 
public class perfectPair381c {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        String[] s = br.readLine().split(" ");
        long x = Long.parseLong(s[0]);
        long y = Long.parseLong(s[1]);
        long m = Long.parseLong(s[2]);
 
        if(x>=m || y>=m){System.out.println("0");return;}
        if(x<=0 && y<=0){System.out.println("-1");return;}
        long moves = 0;
 
        if(x<y){
            if(x<0){
                long temp = (x*-1l)/y + 1;
                moves += temp;
                x = x + (moves*y);
            }
 
            while(y<m && x<m){
                x+=y;
                long temp = y;
                y = x;
                x = temp;
                ++moves;
            }
        }else{
            if(y<0){
                long temp = (y*-1l)/x + 1;
                moves+=temp;
                y = y + (moves*x);
            }
            while(x<m && y<m){
                y+=x;
                long temp = x;
                x = y;
                y = temp;
                ++moves;
            }
        }
       System.out.println(moves);
    }
}