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.InputStreamReader;
import java.util.StringTokenizer;

public class R188qAPair {

	public static void main(String args[] ) throws Exception {
		   
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
	    
	    StringTokenizer st1 = new StringTokenizer(br.readLine());
	    long x = lp(st1.nextToken());
	    long y = lp(st1.nextToken());
	    long m = lp(st1.nextToken());
	    
	    if(x >= m || y >= m){
	    	System.out.println(0);
	    	return;
	    }
	        
	    if(x <= 0 && y <= 0){
	    	System.out.println(-1);
	    	return;
	    }
	    
	    if(x >= 0 && y >= 0){
	    	System.out.println(orange(x,y,m));
	    	return;
	    }
	    
	    if(x >= 0 && y < 0){
	    	long t = (long)Math.ceil(-1.0*y / x);
	    	y += t*x;
	    	System.out.println(t + orange(x,y,m));
	    	return;
	    }
	    
	    if(x < 0 && y >= 0){
	    	long t = (long)Math.ceil(-1.0*x / y);
	    	x += t*y;
	    	System.out.println(t + orange(x,y,m));
	    	return;
	    }
	    
	    throw new Exception();
	}
	
	public static long orange(long x,long y,long m){
		if(x >= m || y >= m)	return 0;
		if(x < y)
			return 1 + orange(x+y,y,m);
		else
			return 1 + orange(x,x+y,m);
	}
	
	public static int ip(String s){
		return Integer.parseInt(s);
	}
	
	public static long lp(String s){
		return Long.parseLong(s);
	}
	
}
