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 Problem318C
{
   boolean DEBUG=false;
   PrintWriter pw;

   public static void main(String[] args) throws Exception
   {
      new Problem318C();
   }
   public Problem318C() throws Exception{
      main();
      pw.close();
   }   
   public void main() throws Exception{
      pw = new PrintWriter(System.out);
      Scanner s = new Scanner(System.in);
      long x=s.nextLong();
      long y=s.nextLong();
      long m=s.nextLong();
      if(x>=m || y>=m){
         pw.println(0);
         return;
      }
      if(x<=0&&y<=0){
         pw.println(-1);
         return;
      }
      if(x>y)
      {
         long z=x;x=y;y=z;
      }
      long start=0;
      if(x<0)
      {
         start=Math.abs(x)/y;
         x+=start*y;
      }
      //go up
      for(long i=0; i<100000; i++)
      {
         if(x>=m || y>=m){
            pw.println(start+i);
            return;
         }
         long z=x+y;
         x=y;
         y=z;
         if(x>y)
         {
            z=x;x=y;y=z;
         }
      }
      pw.println(-1);
   }
   public static StringTokenizer getst(BufferedReader br) throws Exception{
      return new StringTokenizer(br.readLine(), " ");
   }
   public static int nextInt(StringTokenizer st) throws Exception{
      return Integer.parseInt(st.nextToken());
   }

}