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.
//package CF;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

public class CF_C317_PerfectPair {

	public static void main(String[] args) throws IOException {
		BufferedReader bf=new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer ns=new StringTokenizer(bf.readLine());
		long x=Long.parseLong(ns.nextToken());
		long y=Long.parseLong(ns.nextToken());
		long m=Long.parseLong(ns.nextToken());
		
		if(x>=m||y>=m){
			System.out.println(0);
			return;
		}
		
		if((x<=0&&y<=0&&m>=0)||(x>=0&&y>=0&&m<=0)){
			System.out.println(-1);
			return ;
		}
		
		
		if(x<=0&&y<=0&&m>x&&m>y){
			System.out.println(-1);
			return;
		}
		if(x>=0&&y>=0&&m<x&&m<y){
			System.out.println(-1);
			return;
		}
		long cnt=0;
		if(m>0){
			if(x<0){
				long modx=x*-1;
				int r=0;
				if(modx%y!=0)
					r++;
				cnt=modx/y+r;
				if(r==0)
					x=0;
				else
					x=x+((modx/y+1)*y);
			}else{
				if(y<0){
				long mody=y*-1;
				int r=0;
				if(mody%x!=0)
					r++;
				cnt=mody/x+r;
				if(r==0)
					y=0;
				else
					y=y+((mody/x+1)*x);
			}
			}
			while(x<m&&y<m){
				if(x<y)
					x+=y;
				else
					y+=x;
				cnt++;
			}
			
		}else{
			if(x>0){
				int r=0;
				if(x%y!=0)
					r++;
				cnt=x/y+r;
				if(r==0)
					x=0;
				else
					x=x-((x/y+1)*y);
			}
			else{
				if(y>0){
					int r=0;
					if(y%x!=0)
						r++;
					cnt=y/x+r;
					if(r==0)
						y=0;
					else
						y=y-((y/x+1)*x);
				}
			}
			while(x>m&&y>m){
				if(x>y)
					x+=y;
				else
					y+=x;
				cnt++;
			}
			
		}
		System.out.println(cnt);
	}

}
