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.
/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
//package rr;

import com.sun.org.apache.bcel.internal.generic.SWAP;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.Socket;
import java.util.Scanner;

/**
 *
 * @author thn
 */
public class Main {
    
    static long xuli(long x, long y, long m) {
        
        long res = 0;
      //  if (x == 0 && y == 0 && m == 0) return 0;
        if (x >= m || y >= m) return 0;
        if (x <= 0 && y <= 0)  return -1;
        if (x > y)  {
        
            long tmp = x;
            x = y;
            y = tmp;
        } 
            
       
        if ((y - x) / y > 0)
        {
            res = (y - x) / y;
            x += res * y;
        }
        
        while (x < m && y < m) {
            res++;
            long z = x + y;
            if (x > y) y = z;  else x = z;
                
        } 
            
        return res;
    }
    
    public static void main(String[] args) throws IOException{
       
       // Socket socket = new Socket("localhost", 9311);
     //   BufferedWriter out = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
                
                
            Scanner br = new Scanner(new InputStreamReader(System.in));
            
            long x = br.nextLong();
            long y = br.nextLong();
            long m = br.nextLong();
            
            System.out.println(xuli(x, y, m));
                
         //   out.write(x + " " + y + " " + m);
          ///  out.newLine();
          //  out.write("exit");
         //   out.newLine();
        //    out.close();
     
        
    }
}
