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.*;
import java.io.*;

public class Div1A {

	public static void main(String[] args) throws IOException {
		new Div1A().run();
	}

	FastScanner in;
	PrintWriter out;

	void run() throws IOException {
		in = new FastScanner(System.in);
		out = new PrintWriter(System.out, true);
		solve();
		out.close();
	}

	void solve() throws IOException {
		long x = in.nextLong();
		long y = in.nextLong();
		long m = in.nextLong();
		if (x >= m || y >= m) {
			out.println(0);
			System.exit(0);
		}
		if (x <= 0 && y <= 0) {
			out.println(-1);
			System.exit(0);
		}
		long result = 0;
		if (x < y) {
			x ^= y;
			y ^= x;
			x ^= y;
		}
		if (y < 0) {
			long cnt = (Math.abs(y) + x - 1) / x;
			result += cnt;
			y += cnt * x;
		}
		while (x < m) {
			y += x;
			x ^= y;
			y ^= x;
			x ^= y;
			result++;
		}
		out.println(result);
	}

	static class FastScanner {

		BufferedReader br;
		StringTokenizer st;

		FastScanner(InputStream in) {
			br = new BufferedReader(new InputStreamReader(in));
			st = null;
		}

		String next() throws IOException {
			while (st == null || !st.hasMoreTokens())
				st = new StringTokenizer(br.readLine());
			return st.nextToken();
		}
		
		String nextLine() throws IOException {
			if (st == null || !st.hasMoreTokens())
				return br.readLine();
			StringBuilder result = new StringBuilder(st.nextToken());
			while (st.hasMoreTokens()) {
				result.append(" ");
				result.append(st.nextToken());
			}
			return result.toString();
		}

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

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

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

	}

}
