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.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.StringTokenizer;
public class cfvc9
{
	static BufferedReader reader;
    static StringTokenizer tokenizer;
    static void init(InputStream input) 
    {
        reader = new BufferedReader( new InputStreamReader(input) );
        tokenizer = new StringTokenizer("");
    }
    static String next() throws IOException
    {
        while ( ! tokenizer.hasMoreTokens() )
        {
            tokenizer = new StringTokenizer(reader.readLine() );
        }
        return tokenizer.nextToken();
    }

    static long nextInt() throws IOException 
    {
        return Long.parseLong( next() );
    }
	static PrintWriter writer;
	static void outit(OutputStream outputStream)
	{
		writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
	}
	static void print(Object...objects) {
		for (int i = 0; i < objects.length; i++) {
			if (i != 0)
				writer.print(' ');
			writer.print(objects[i]);
		}
	}

	static void println(Object...objects) {
		print(objects);
		writer.println();
	}

	static void close() {
		writer.close();
	}

	static void flush() {
		writer.flush();
	}
    public static void main(String [] args) throws IOException
    {
    	init(System.in) ;
    	outit(System.out) ;
//    	int t = nextInt() ;
//    	for(int i = 0 ; i<t ; i++)
//    	{
    		output() ;
//    	}
        flush();
        close();
    }
    public static void output() throws IOException
    {
    	long x = nextInt() ;
    	long y = nextInt() ;
    	long k = nextInt() ;
    	long ctr =  0 ;
    	if(x<=0&&y<=0)
    	{
    		if(x>=k||y>=k)
    		{
    			println(0) ;
    		}
    		else
    		{
    			println(-1) ;
    		}
    	}
    	else
    	{
    		if(x>=k||y>=k)
    		{
    			println(0) ;
    		}
    		else
    		{
    		if(k>=0)
    		{
    		if(x>0&&y<0)
    		{
    			ctr = ctr - y/x ;
    			y = y - x*(y/x) ;
    		}
    		if(x<0&&y>0)
    		{
    			ctr = ctr - x/y ;
    			x = x - y*(x/y) ;    			
    		}
    		}
    		else
    		{
    			if(x>0&&y<0)
        		{
        			ctr = ctr - (y-k)/x ;
        			y = y - x*((y-k)/x) ;
        		}
        		if(x<0&&y>0)
        		{
        			ctr = ctr - (x-k)/y ;
        			x = x - y*((x-k)/y) ;    			
        		}
    		}
    	while(true)
    	{
    		if(x>=k||y>=k)
    		{
    			println(ctr) ;
    			break ;
    		}
    		if(x>y)
    		{
    			y = x+y ;
    		}
    		else
    		{
    			x = x+y ;
    		}
    		ctr++ ;
    	}
    	}
    	}
    }
    }