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.Scanner;

public class Principal {

	public static void main(String[] args) {
		long x, y, m, answer;

		Scanner leitor = new Scanner(System.in);
		x = leitor.nextLong();
		y = leitor.nextLong();
		m = leitor.nextLong();

		answer = perfectPair(x, y, m);
		System.out.println(answer);

	}

	public static long perfectPair(long x, long y, long m) {
		long qntDeOperacoesRealizadas = 0, passosParaNaoSerNegativo = 0, aux = 0;

		if (x >= m || y >= m)
			return 0;

		if (m >= 0)
			if (x <= 0 && y <= 0)
				return -1;

		if ((m <= 0) && (x < 0 && y < 0))
			return -1;

		if (x < y) {
			aux = x;
			x = y;
			y = aux;
		}

		if (y < 0) {
			passosParaNaoSerNegativo = (Math.abs(y) + x - 1) / x;
			y += passosParaNaoSerNegativo * x;
			qntDeOperacoesRealizadas += passosParaNaoSerNegativo;
		}

		while ((x < m) && (y < m)) {
			if (y < x)
				y = y + x;
			else
				x = x + y;
			qntDeOperacoesRealizadas++;
		}

		return qntDeOperacoesRealizadas;
	}
}
