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.*;
import java.math.*;

public class Main{
	
	public void solve(){
		Long x, y, m;
		x = in.nextLong();
		y = in.nextLong();
		m = in.nextLong();
		
		if(y < x){
			Long l = x;
			x = y;
			y = l;
		}
		
		if(m <= y){
			out.print(0);
			return;
		}
		
		if(y <= 0){
			out.print(-1);
			return;
		}
		
		Long cancelLong = Math.max(0, - x / y - 5);
		Long cnt = cancelLong;
		x += y * cancelLong;
		
		while(y < m){
			cnt++;
			x += y;
			if(y < x){
				Long l = x;
				x = y;
				y = l;
			}
		}
		
		out.println(cnt);
	}
	
	
	
	MyInput in;
	PrintWriter out;
	
	public void run(){
		in = new MyInput(System.in);
		out = new PrintWriter(System.out);
		solve();
		out.close();
	}
	
	public static void main(String[] args){
		new Main().run();
	}
}

class MyInput{
	BufferedReader in;
	StringTokenizer token;
	
	
	MyInput(InputStream is){
		try{
			in = new BufferedReader(new InputStreamReader(is));
		}catch(Exception e){ e.printStackTrace(); }
		
	}
	
	String nextToken(){
		while(token == null || !token.hasMoreTokens()){
			try{
				token = new StringTokenizer(in.readLine());
			}catch(Exception e){ e.printStackTrace(); }
		}
		return token.nextToken();
	}
	
	int nextInt(){
		return Integer.parseInt(nextToken());
	}
	
	long nextLong(){
		return Long.parseLong(nextToken());
	}
	
	double nextDouble(){
		return Double.parseDouble(nextToken());
	}
}




















