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.*;
public class a317
{
    public static void main(String args[])throws IOException
    {
        InputStreamReader read=new InputStreamReader(System.in);
        BufferedReader in=new BufferedReader(read);
        String s;
       // System.out.println("Enter");
        s=in.readLine();
        StringTokenizer st=new StringTokenizer(s);
        long x,y,m,sum=0,t,c=0;
        x=Long.parseLong(st.nextToken());
        y=Long.parseLong(st.nextToken());
        m=Long.parseLong(st.nextToken());
        if(x>y)
        {
            t=x;
            x=y;
            y=t;
        }
        if(y==0 && m>0)
        {
            System.out.println("-1");
            System.exit(0);
        }
        else
        if(x<0 && y<0 && m>y)
        {
            System.out.println("-1");
            System.exit(0);
        }
        else
        {
            while(true)
            {
                if(x>=m || y>=m)
                {
                    System.out.println(sum);
                    System.exit(0);
                }
                if(c==0)
                {
                    if(x<0)
                    {
                        t=(-x/y);
                        x=x+(t+1)*y;
                        sum+=(t+1);
                        c++;
                    }
                }
                if(x<=y)
                {
                    x=x+y;
                    sum++;
                }
                else if(y<x)
                {
                    y=y+x;
                    sum++;
                }
            }
        }
    }
}

        
        
        