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.*;

//Codeforces
public class Codeforces1 {
	private static MyScanner in;
	private static PrintStream out;
	private static boolean LOCAL_TEST = false;

	private static void solve() throws IOException {
		long ops;
		long x = in.nextLong();
		long y = in.nextLong();
		long m = in.nextLong();
		ops = 0;
		long sumxy;
		while (x < m && y < m) {
			if (x < 0 && y < 0)
				break;

			sumxy = x + y;
			if (Math.signum(x) * Math.signum(y) < 0) {
				long bx = Math.max(x, y);
				long by = Math.min(x, y);
				long dops = -by / bx;
				ops += dops;
				by += bx * dops;
				x = bx;
				y = by;
			}
			if (x >= m || y >= m)
				break;

			if (x < y) {
				x = x + y;
			} else {
				y = x + y;
			}
			if ((x + y) > sumxy) {
				ops++;
				continue;
			} else
				break;
		}
		if (x < m && y < m)
			ops = -1;

		out.println(ops);
	}

	public static void main(String[] args) throws IOException {
		// helpers for input/output
		out = System.out;
		try {
			String cname = System.getenv("COMPUTERNAME");
			if (cname != null)
				LOCAL_TEST = true;
		} catch (Exception e) {
		}
		if (LOCAL_TEST) {
			in = new MyScanner("E:\\zin.txt");
		} else {
			boolean usingFileForIO = false;
			if (usingFileForIO) {
				// using input.txt and output.txt as I/O
				in = new MyScanner("input.txt");
				out = new PrintStream("output.txt");
			} else {
				in = new MyScanner();
				out = System.out;
			}
		}

		solve();
	}

	// =====================================
	static class MyScanner {
		BufferedReader bufReader;
		StringTokenizer strTok;

		public MyScanner() throws IOException {
			bufReader = new BufferedReader(new InputStreamReader(System.in));
			strTok = new StringTokenizer("");
		}

		public MyScanner(String inputFile) throws IOException {
			bufReader = new BufferedReader(new InputStreamReader(new FileInputStream(
					inputFile)));
			strTok = new StringTokenizer("");
		}

		String GetNextToken() throws IOException {
			if (!strTok.hasMoreTokens())
				strTok = new StringTokenizer(bufReader.readLine());
			return strTok.nextToken();
		}

		public int nextInt() throws IOException {
			return Integer.valueOf(GetNextToken());
		}

		public long nextLong() throws IOException {
			return Long.valueOf(GetNextToken());
		}

		public double nextDouble() throws IOException {
			return Double.valueOf(GetNextToken());
		}

		public String nextString() throws IOException {
			return GetNextToken();
		}

		public String nextLine() throws IOException {
			return bufReader.readLine();
		}

		public int countTokens() {
			return strTok.countTokens();
		}

		public boolean hasMoreTokens() {
			return strTok.hasMoreTokens();
		}
	}

}