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.InputStreamReader;
import java.util.Arrays;
import java.util.StringTokenizer;

public class ProC {
	public static void main(String[] args) {
		MyScanner cin = new MyScanner();

		long x = cin.nextLong();
		long y = cin.nextLong();
		long m = cin.nextLong();

		long min = Long.min(x, y);
		long max = Long.max(x, y);

		long ans = solve(min, max, m);
		System.out.println(ans);
	}

	private static long solve(long min, long max, long m) {
		if (max >= m) {
			return 0;
		} else if (min + max <= min)
			return -1;

		long count = 0;
		long[] temp = new long[3];
		if (min < 0) {
			count += (max - min) / max;
			min += count * max;
		}

		while (max < m) {
			count++;
			temp[0] = min;
			temp[1] = max;
			temp[2] = min + max;
			Arrays.sort(temp);
			min = temp[1];
			max = temp[2];
			if (min < 0 && max < 0)
				return -1;
		}

		return count;
	}

	private static class MyScanner {
		BufferedReader br;
		StringTokenizer st;

		public MyScanner() {
			br = new BufferedReader(new InputStreamReader(System.in));
		}

		String next() {
			while (st == null || !st.hasMoreElements()) {
				try {
					st = new StringTokenizer(br.readLine());
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
			return st.nextToken();
		}

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

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