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.math.BigInteger;
import java.util.Arrays;
import java.util.Scanner;


public class Main {

	public static void main(String args[])
	{
		Scanner s=new Scanner(System.in);
		
	String temp[]=s.nextLine().split(" ");
	BigInteger bi1=new BigInteger(temp[0]);
	BigInteger bi2=new BigInteger(temp[1]);
	BigInteger bi3=new BigInteger(temp[2]);
	BigInteger zero=new BigInteger("0");
	BigInteger one=new BigInteger("1");
	BigInteger lar;
	
		if(bi1.compareTo(bi2)>0)
			lar=bi1;
		else
			lar=bi2;
			if(lar.compareTo(bi3)>=0)
				System.out.println("0");
			else if(lar.compareTo(zero)<=0)
				System.out.println("-1");
			else
			{BigInteger ans=new BigInteger("0");
			if(bi1.compareTo(zero)<0)
			{BigInteger tmp=bi1.abs().divide(bi2);
				bi1=bi1.add(bi2.multiply(tmp));
				ans=ans.add(tmp);
			}
			while(bi1.compareTo(zero)<0)
			{	ans=ans.add(one);
			
			
			bi1=bi1.add(bi2);}
			if(bi2.compareTo(zero)<0)
			{BigInteger tmp=bi2.abs().divide(bi1);
				bi2=bi2.add(bi1.multiply(tmp));
				ans=ans.add(tmp);
			}
			while(bi2.compareTo(zero)<0)
				{bi2=bi2.add(bi1);ans=ans.add(one);}
				
				while(lar.compareTo(bi3)<0)
				{
					if(lar.compareTo(bi1)>0)
						{bi1=bi1.add(bi2);lar=bi1;}
					else
					{bi2=bi2.add(bi1);lar=bi2;}
					ans=ans.add(one);
				}
				System.out.println(ans);
				
				
				
			}
		
	
	 
	}
}
