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.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class C_2013_Jun_14_Div2 {
  public static void main(String[] args) throws IOException {
    BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
    String[] as = reader.readLine().split("\\s+");
    long x = Long.parseLong(as[0]);
    long y = Long.parseLong(as[1]);
    long m = Long.parseLong(as[2]);
    long count = 0;
    while (x < m && y < m) {
      long sum = x + y;

      long max = Math.max(x, y);
      long min = Math.min(x, y);
      if (max <= 0) {
        System.out.println("-1");
        return;
      }
      if (min < 0) {
        long k = -(min / max);
        if (k > 0) {
          count += k;
          x = max;
          y = min + k * max;
          continue;
        }
      }
      x = sum;
      y = max;
      count++;
    }
    System.out.println(count);
  }
}
