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.math.BigInteger;
import java.util.*;

public class A
{
	String line;
	StringTokenizer inputParser;
	BufferedReader is;
	FileInputStream fstream;
	DataInputStream in;
	String FInput="";
	
	void openInput(String file)
	{

		if(file==null)is = new BufferedReader(new InputStreamReader(System.in));//stdin
		else
		{
			try{
		
				
			fstream = new FileInputStream(file);
			in = new DataInputStream(fstream);
			is = new BufferedReader(new InputStreamReader(in));
			}catch(Exception e)
			{
				System.err.println(e);
			}
		}

	}
	
	void readNextLine()
	{
		try {
			line = is.readLine();
			inputParser = new StringTokenizer(line, " ");
			//System.err.println("Input: " + line);
		} catch (IOException e) {
			System.err.println("Unexpected IO ERROR: " + e);
		}	
		catch (NullPointerException e)
		{
			line=null;
			
		}
		
	}
	
	int NextInt()
	{
		String n = inputParser.nextToken();
		int val = Integer.parseInt(n);
		
		//System.out.println("I read this number: " + val);
		return val;
	}
	
	long NextLong()
	{
		String n = inputParser.nextToken();
		long val = Long.parseLong(n);
		
		//System.out.println("I read this number: " + val);
		return val;
	}
	
	double NextDouble()
	{
		String n = inputParser.nextToken();
		double val = Double.parseDouble(n);
		
		//System.out.println("I read this number: " + val);
		return val;
	}
	
	String NextString()
	{
		String n = inputParser.nextToken();
		return n;
	}
	
	void closeInput()
	{
		try {
			is.close();
		} catch (IOException e) {
			System.err.println("Unexpected IO ERROR: " + e);
		}
			
	}
	
	
	public static void main(String [] argv)
	{
		//String filePath="input.txt";
        String filePath=null;
		if(argv.length>0)filePath=argv[0];
		new A(filePath);
	}
	
	public void readFInput()
	{
		for(;;)
		{
			try
			{
				readNextLine();
				FInput+=line+" ";
			}
			catch(Exception e)
			{
				break;
			}
		}
		inputParser = new StringTokenizer(FInput, " ");
	}

	public A(String inputFile)
	{
		openInput(inputFile);
		readNextLine();
    	long x=NextLong(), y=NextLong(), m=NextLong();
    	long ret=0;
    	if(x<m&&y<m)
    	{
    		if(x<=0&&y<=0)ret=-1;
    		else
    		{
    			if(x>y)
    			{
    				long t=x;
    				x=y;
    				y=t;
    			}
    			if(x<0)
    			{
    				ret=(-1*x)/y;
    				x+=ret*y;
    			}
    			while(x<m&&y<m)
    			{
    				if(x<y)x=x+y;
    				else y=x+y;
    				ret++;
    			}
    		}
    	}
    	
	    System.out.println(ret);
    	
    	
		closeInput();			
	}

}