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.util.StringTokenizer;


public class C {
    public static void main(String[] args) {
        MyScanner sc = new MyScanner();
        long a = sc.nextLong();
        long b = sc.nextLong();
        long m = sc.nextLong();
        long x = Math.min(a, b);
        long y = Math.max(a, b);

        if (m <= x || m <= y) {
            System.out.println(0);
            return;
        }
        if (x <= 0 && y <= 0) {
            System.out.println(-1);
            return;
        }
        
        long count = 0;
        if (x < 0) {
            count += Math.abs(x / y) + 1;
            x += y * count;
        }
        
        while (Math.max(x, y) < m) {
            if (x < y) {
                x = x + y;
            }
            else {
                y = x + y;
            }
            count++;
        }
        System.out.println(count);
    }

    


    
    
    
    
    
    public static class MyScanner {
        BufferedReader br;
        StringTokenizer st;
 
        public MyScanner() {
           br = new BufferedReader(new InputStreamReader(System.in));
        }
 
        String next() {
            while (st == null || !st.hasMoreElements()) {
                  try {
                        st = new StringTokenizer(br.readLine());
                  } catch (IOException e) {
                        e.printStackTrace();
                  }
            }
            return st.nextToken();
        }
 
        int nextInt() {
            return Integer.parseInt(next());
        }
 
        long nextLong() {
            return Long.parseLong(next());
        }
 
        double nextDouble() {
            return Double.parseDouble(next());
        }
 
        String nextLine(){
            String str = "";
        try {
           str = br.readLine();
        } catch (IOException e) {
           e.printStackTrace();
        }
        return str;
        }
    }
}
