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.util.*;
public class cf317a {
  public static void main(String[] args) {
    Scanner in = new Scanner(System.in);
    long[] v = new long[2];
    for(int i=0; i<2; i++)
      v[i] = in.nextLong();
    Arrays.sort(v);
    long m = in.nextLong();
    if(v[1] >= m) {
      System.out.println(0);
      return;
    }
    if(v[1] <= 0) {
      System.out.println("-1");
      return;
    }
    long ans = 0;
    if(v[0] < 0) {
      ans += (-v[0])/v[1];
      v[0] += ans*v[1];
      Arrays.sort(v);
    }
    while(v[1] < m) {
      v[0] += v[1];
      Arrays.sort(v);
      ans++;
    }
    System.out.println(ans);
  }
}
