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 Solution {
   BufferedReader in;
   StringTokenizer str;
   PrintWriter out;
   String SK;
   String next() throws IOException {
      while ((str == null) || (!str.hasMoreTokens())) {
      SK = in.readLine();
      if (SK == null)
      return null;
      str = new StringTokenizer(SK);
      }
      return str.nextToken();
   }
   int nextInt() throws IOException {
      return Integer.parseInt(next());
   }
   double nextDouble() throws IOException {
      return Double.parseDouble(next());
   }
   long nextLong() throws IOException {
      return Long.parseLong(next());
   }
   char[] charArray() throws IOException{
      return next().toCharArray();
   }
   public static void main(String[] args) throws IOException {
      new Solution().run();
   }
   void run() throws IOException {
      in = new BufferedReader(new InputStreamReader(System.in));
      out = new PrintWriter(System.out);
      //in = new BufferedReader(new FileReader("input.txt"));
      //out = new PrintWriter("output.txt");
      solve();
      out.close();
   }
   void solve() throws IOException {
      long x=nextLong();
      long y=nextLong();
      long m=nextLong();
      if(x>=m || y>=m){
         out.println(0);
         return;
      }
      if(x<=0 && y<=0){
         out.println(-1);
         return;
      }
      long a=Math.min(x,y);
      long b=Math.max(x,y);
      long count=0;
      if(a<0){
         long min=0;
         long max=0;
         if(a/b==0){
            count=1;
            min=b+a;
            max=b;
         }
         else{
            count = -1 * (-1 + a / b);
            min=Math.min(b,count*b+a);
            max=Math.max(b,b*count+a);
         
         }
         while(max<m){
            count++;
            long temp=min;
            min=max;
            max=max+temp;
         }
      }
      else{
         long max=b;
         long min=a;
         while(max<m){
            count++;
            long tem=min;
            min=max;
            max=max+tem;
         }
      }
      out.println(count);




   }
   
}
