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.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.LinkedList;
import java.util.List;
import java.util.PriorityQueue;
import java.util.Queue;
import java.util.SortedSet;
import java.util.StringTokenizer;
import java.util.TreeSet;

public class Code {
    public static void main(String[] args) {
        // Use the Scanner class
        MyScanner sc = new MyScanner();
        out = new PrintWriter(new BufferedOutputStream(System.out));

        long x = sc.nextLong();
        long y = sc.nextLong();

        long m = sc.nextLong();

        if (!solution_exists(x,y,m)) {
            System.out.println("-1");
            return;
        }
        if (Math.max(x, y) >= m) {
            System.out.println(0);
            return;
        }
        long n = 0;
        if (x < 0 || y < 0) {
            long neg = y < 0 ? y : x;
            long oth = x > 0 ? x : y;
            n = (-1*neg)/oth;
            x = oth;
            y = n*oth + neg;
        }

        long min = Math.min(x, y);
        long max = Math.max(x, y);
        int i = 0;
        while (max < m) {
            x = max + min;
            y = max;
            max = Math.max(x, y);
            min = Math.min(x, y);
            i++;
        }
        System.out.println(n + i);
    }


    static boolean solution_exists(long a, long b, long m) {
        if (Math.max(a, b) >= m) {
            return true;
        }
        return a + b > Math.min(a, b);
    }

    public static PrintWriter out;

    //-----------MyScanner class for faster input----------
    public static class MyScanner {
       BufferedReader br;
       StringTokenizer st;

       public MyScanner() {
          br = new BufferedReader(new InputStreamReader(System.in));
       }

       String next() {
           while (st == null || !st.hasMoreElements()) {
               try {
                   st = new StringTokenizer(br.readLine());
               } catch (IOException e) {
                   e.printStackTrace();
               }
           }
           return st.nextToken();
       }

       int nextInt() {
           return Integer.parseInt(next());
       }

       long nextLong() {
           return Long.parseLong(next());
       }

       double nextDouble() {
           return Double.parseDouble(next());
       }

       String nextLine(){
           String str = "";
       try {
          str = br.readLine();
       } catch (IOException e) {
          e.printStackTrace();
       }
       return str;
       }

    }
}