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.*;
import java.util.*;

public class C188
{	
	public C188()
	{
		Scanner in = new Scanner(System.in);
		StringTokenizer st = new StringTokenizer(in.nextLine());
		
		long x = Long.parseLong(st.nextToken());
		long y = Long.parseLong(st.nextToken());
		long m = Long.parseLong(st.nextToken());
		
		if(x <= 0 && y <= 0 && x < m && y < m)
			System.out.println(-1);
		else if(x > m || y > m)
			System.out.println(0);
		else
		{
			long moves = 0;
			long min = Math.min(x, y);
			y = Math.max(x,  y);
			x = min;
			
			if(m > 0 && x < 0 && y > 0)
			{
				long count = Math.abs(x / y);
				
				x += count * y;
				moves += count;
			}
			else if(m > 0 && x < 0 && y > 0)
			{
				long count = Math.abs((x - m) / y);
				
				x += count * y;
				moves += count;
			}
			
			while(x < m && y < m)
			{
				if(x < y)
					x += y;
				else
					y += x;
				moves++;
			}
			System.out.println(moves);
		}
	}
	
	public static void main(String[] args)
	{
		new C188();
	}
}
