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.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.StringTokenizer;

public class C188D2C {
	public static void main(String[] args) {
		InputReader in = new InputReader(System.in);
		PrintWriter out = new PrintWriter(System.out);
		long x = in.nextLong(), y = in.nextLong(), m = in.nextLong();
		if (x >= m || y >= m) {
			out.println(0);
		} else if (x <= 0 && y <= 0) {
			out.println(-1);
		} else {
			long res = 0;
			long[] f = new long[3];
			if (x < 0) {
				res += Math.abs(x / y);
				x += res * y;
			} else if (y < 0) {
				res += Math.abs(y / x);
				y += res * x;
			}
			f[0] = Math.min(x, y);
			f[1] = Math.max(x, y);
			while (true) {
				res++;
				f[2] = f[0] + f[1];
				if (f[2] >= m) {
					break;
				}
				f[0] = Math.min(f[1], f[2]);
				f[1] = Math.max(f[1], f[2]);
			}
			out.println(res);
		}
		out.flush();
	}

	static class InputReader {
		public BufferedReader reader;
		public StringTokenizer tokenizer;

		public InputReader(InputStream stream) {
			reader = new BufferedReader(new InputStreamReader(stream));
			tokenizer = null;
		}

		public String next() {
			while (tokenizer == null || !tokenizer.hasMoreTokens()) {
				try {
					tokenizer = new StringTokenizer(reader.readLine());
				} catch (IOException e) {
					throw new RuntimeException(e);
				}
			}
			return tokenizer.nextToken();
		}

		public long nextLong() {
			return Long.parseLong(next());
		}
		
		public int nextInt() {
			return Integer.parseInt(next());
		}
	}
}