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.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.io.PrintStream;
import java.util.HashMap;
import java.util.Map;
import java.util.StringTokenizer;

/*
public class _317A {

}

 */

public class _317A {
	public void solve() throws FileNotFoundException {
		InputStream inputStream = System.in;

		InputHelper inputHelper = new InputHelper(inputStream);

		PrintStream out = System.out;

		//actual solution
		long x = inputHelper.readLong();
		long y = inputHelper.readLong();
		long m = inputHelper.readLong();
		
		if(Math.max(x, y) >= m)
		{
			System.out.println("0");
			return;
		}
		
		if(x <= 0 && y <= 0)
		{
			System.out.println("-1");
			return;
		}

		long ans = 0;
		if(x < 0)
		{
			ans += (long)Math.ceil((double)Math.abs(x) / y);
			x += (ans * y);
		}
		else if(y < 0)
		{
			ans += (long)Math.ceil((double)Math.abs(y) / x);
			y += (ans * x);
		}
		
		while(x < m && y < m)
		{
			if(x <= y)
			{
				x = x + y;
			}
			else
			{
				y = x + y;
			}
			ans++;
		}
		
		System.out.println(ans);
		//end here
	}

	public static void main(String[] args) throws FileNotFoundException {
		(new _317A()).solve();
	}

	class InputHelper {
		StringTokenizer tokenizer = null;
		private BufferedReader bufferedReader;

		public InputHelper(InputStream inputStream) {
			InputStreamReader inputStreamReader = new InputStreamReader(
					inputStream);
			bufferedReader = new BufferedReader(inputStreamReader, 16384);
		}

		public String read() {
			while (tokenizer == null || !tokenizer.hasMoreTokens()) {
				try {
					String line = bufferedReader.readLine();
					if (line == null) {
						return null;
					}
					tokenizer = new StringTokenizer(line);
				} catch (IOException e) {
					e.printStackTrace();
				}
			}

			return tokenizer.nextToken();
		}

		public Integer readInteger() {
			return Integer.parseInt(read());
		}

		public Long readLong() {
			return Long.parseLong(read());
		}
	}
}