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.*;

public class Main{

    BufferedReader in;
    StringTokenizer str = null;
    PrintWriter out;

    private String next() throws Exception{
    	if (str == null || !str.hasMoreElements())
    	    str = new StringTokenizer(in.readLine());
    	return str.nextToken();
    }
    
    private int nextInt() throws Exception{
	return Integer.parseInt(next());
    }

    private long nextLong() throws Exception{
	return Long.parseLong(next());
    }
    
    public void run() throws Exception{
    	in = new BufferedReader(new InputStreamReader(System.in));
    	out = new PrintWriter(System.out);

	long x = nextLong(), y = nextLong(), m = nextLong();

	if (Math.max(x, y) >= m){
	    out.println(0);
	    out.close();
	    return;
	}
	if (x <= 0 && y <= 0){
	    out.println(-1);
	    out.close();
	    return;
	}

	if (x > y){
	    long c = x;
	    x = y;
	    y = c;
	}
	long t = 0;
	
	if (x < 0) {
	    x = -x;
	    t = x/y+1;
	    if (x % y == 0){
		t--;
		x = 0;
	    }else{
		x = y - x%y;
	    }
	}
	
	while(Math.max(x, y) < m) {
	    long a[] = new long[]{x, y, x + y};
	    Arrays.sort(a);
	    x = a[1];
	    y = a[2];
	    t++;
	}
	out.println(t);
	out.close();
	return;
    }

    public static void main(String args[]) throws Exception{
	   new Main().run();
    }
}