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 static java.lang.Math.max;

import java.io.*;
import java.util.*;

public class A {

	static void solve() throws IOException {
		long x = nextLong(), y = nextLong();
		long m = nextLong();
		long steps = steps(x, y, m);
		out.println(steps);
	}

	private static long steps(long x, long y, long m) {
		if (x >= m || y >= m) {
			return 0;
		}
		if (x <= 0 && y <= 0) {
			return -1;
		}
		if (x < y) {
			long t = x;
			x = y;
			y = t;
		}
		long steps = 0;
		if (y < 0) {
			long stepsToMakeNonNegative = (Math.abs(y) + x - 1) / x;
			y += stepsToMakeNonNegative * x;
			steps += stepsToMakeNonNegative;
		}
		while (x < m && y < m) {
			long nx = max(x, y);
			long ny = x + y;

			x = nx;
			y = ny;
			++steps;
		}
		return steps;
	}

	static BufferedReader br;
	static StringTokenizer st;
	static PrintWriter out;

	public static void main(String[] args) throws IOException {
		InputStream input = System.in;
		PrintStream output = System.out;
		File file = new File("a.in");
		if (file.exists() && file.canRead()) {
			input = new FileInputStream(file);
		}
		br = new BufferedReader(new InputStreamReader(input));
		out = new PrintWriter(output);
		solve();
		out.close();
	}

	static long nextLong() throws IOException {
		return Long.parseLong(nextToken());
	}

	static double nextDouble() throws IOException {
		return Double.parseDouble(nextToken());
	}

	static int nextInt() throws IOException {
		return Integer.parseInt(nextToken());
	}

	static String nextToken() throws IOException {
		while (st == null || !st.hasMoreTokens()) {
			String line = br.readLine();
			if (line == null) {
				return null;
			}
			st = new StringTokenizer(line);
		}
		return st.nextToken();
	}
}
