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.*;
import java.lang.*;
import java.math.BigInteger;


public class Main {
  


	public static void main(String[] args) throws Exception
	{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		int t,ca,i,j;
		String[] my;
		String line = br.readLine();
        my = line.split(" ");
        long n,m,k;
        my = line.split(" ");
        n = Long.parseLong(my[0]);
        m =Long.parseLong(my[1]);
        k =Long.parseLong(my[2]);
          long x ;
        if(n < m)
        {
            x = n;
            n = m;
            m = x;
        }
        long st = 0;
        int valid = 0;
        while(true)
        {
            if(n >= k){valid = 1;break;}
            if(n<=0)break;
            if(m<0)
            {
                long mi = -m;
                long xx = mi/n;
                st+= xx;
                m = m + xx*n;
            }
          x = m + n;
          if(x <= m)break;
          m = n;
          n = x;
          st++;
          if(n < m){
              x = m;
              m=n;
              n=x;
          }
          
        }
        if(valid==0)st = -1;
        System.out.println(st);
        }
    
}
class ut implements Comparator<Team>{
    public int compare(Team first, Team other)
    {
          if(first.pr > other.pr)return -1;
        if(first.pr < other.pr)return 1;
        if(first.ti < other.ti)return -1;
        if(first.ti > other.ti)return 1;
        if(first.in < other.in)return -1;
        if(first.in > other.in)return 1;
        return 0;
    }
}
class Team implements Comparable{
    int pr,ti,in;
    public Team(int a, int b, int c)
    {
        pr = a;
        ti = b;
        in = c;
    }
    public String toString()
    {
        return pr + " " + ti + " " + in+ "\n";
    }
    public int compareTo(Object obj)
    {
        Team other = (Team)obj;
        if(pr > other.pr)return -1;
        if(pr < other.pr)return 1;
        if(ti < other.ti)return -1;
        if(ti > other.ti)return 1;
        if(in < other.in)return -1;
        if(in > other.in)return 1;
        return 0;
    }
}

