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.util.*;
import java.io.*;
import java.math.*;

public class C2 {
    public static Scanner scan = new Scanner(System.in);
    public static boolean bg = false;

    public static void main(String[] args) throws Exception {
        long n1 = Long.parseLong(scan.next());
        long n2 = Long.parseLong(scan.next());
        long n3 = Long.parseLong(scan.next());
        ArrayList<Long> t1 = new ArrayList();
        t1.add(n1);
        t1.add(n2);
        
        
        Collections.sort(t1);
        if (t1.get(1)>=n3){
            System.out.println(0);
            System.exit(0);
        }
        if (n1+n2<=t1.get(0) ){
            System.out.println(-1);
            System.exit(0);
        }
        
        long count = 0;
        if (t1.get(0)<0&&t1.get(1)>0){
            if (n3>=0){
                count+=(-t1.get(0))/t1.get(1);
                long qq1 = (-t1.get(0))/t1.get(1);
                long old = t1.remove(0);
                t1.add(old+(qq1)*t1.get(0) );
            }
        }
        if (bg) System.out.println(count);
        for (;;){
            Collections.sort(t1);
            if (bg) System.out.println(t1);
            if (t1.get(1)>=n3){
                System.out.println(count);
                System.exit(0);
            }
            long add = t1.get(0)+t1.get(1);
            t1.remove(0);
            t1.add(add);
            Collections.sort(t1);
            count++;
        }
        
    }
}
/*
int n1 = Integer.parseInt(scan.next());
int n2 = Integer.parseInt(scan.next());
String str1 = scan.nextLine();
for (int i=0;i<n1;i++){
    int k1 = Integer.parseInt(scan.next());
}
System.out.println();
*/
