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.*;
import java.util.*;
import java.math.*;

public class Main implements Runnable {

	public void _main() throws IOException {
		long x = nextLong();
		long y = nextLong();
		long m = nextLong();
		if (good(x, y, m)) {
			out.println(0);
			return;
		}
		if (x <= 0 && y <= 0) {
			out.println(-1);
			return;
		}
		long add = 0;
		if (x < 0 || y < 0) {
			long nx = Math.max(x, y);
			long ny = Math.min(x, y);
			x = Math.abs(nx);
			y = Math.abs(ny);
			long k = (y + x - 1) / x;
			if (m < 0) {
				k = (m + y + x - 1) / x;
			}
			add += k;
			y = k*x - y;
		}
		for (int i = 0; ; i++) {
			if (good(x, y, m)) {
				out.println(i + add);
				return;
			}
			long nx = x + y;
			long ny = Math.max(x, y);
			x = nx;
			y = ny;
		}
	}

	private boolean good(long x, long y, long m) {
		return x >= m || y >= m;
	}


	private BufferedReader in;
	private PrintWriter out;
	private StringTokenizer st;

	private String next() throws IOException {
		while (st == null || !st.hasMoreTokens()) {
			String rl = in.readLine();
			if (rl == null)
				return null;
			st = new StringTokenizer(rl);
		}
		return st.nextToken();
	}

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

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

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

	public static void main(String[] args) {
		Locale.setDefault(Locale.UK);
		new Thread(new Main()).start();
	}

	public void run() {
		try {
			in = new BufferedReader(new InputStreamReader(System.in));
			out = new PrintWriter(System.out);
			//in = new BufferedReader(new FileReader("a.in"));
			//out = new PrintWriter(new FileWriter("a.out"));

			_main();

			out.close();
		} catch (Exception e) {
			e.printStackTrace();
			System.exit(202);
		}
	}

}
