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.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.PriorityQueue;
import java.util.Queue;
import java.util.Scanner;

public class ProblemA {
	public static long doit(long x, long y, long m, long cur) {
		if (x >= m || y >= m) {
			return 0;
		}
		if (x <= 0 && y <= 0) {
			return -1;
		}
		
		long larger = Math.max(x, y);
		long smaller = Math.min(x, y);
		if (larger > 0 && smaller < 0) {
			long pl = ((-smaller)+larger-1) / larger;
			long ret = doit(larger, smaller+larger*pl, m, cur+1);
			if (ret >= 0) {
				return ret + pl; 
			}
			return -1;
		}

		long ret = doit(larger, larger+smaller, m, cur+1);
		if (ret >= 0) {
			return ret + 1;
		}
		return -1;
	}

	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		PrintWriter out = new PrintWriter(System.out);

		long x = in.nextLong();
		long y = in.nextLong();
		long m = in.nextLong();
		
		out.println(doit(x, y, m, 0));
		out.flush();
	}

	public static void debug(Object... o) {
		System.err.println(Arrays.deepToString(o));
	}
}
