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.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.PriorityQueue;
import java.util.Queue;
import java.util.Scanner;
import java.util.StringTokenizer;
import java.util.concurrent.LinkedBlockingDeque;

import javax.swing.border.Border;

public class a {

	public static long mod = (long) Math.pow(10, 9) + 7;

	private static class node {
		long a;
		long b;
		int move;

		node(long a, long b, int val) {
			this.a = a;
			this.b = b;
			this.move = val;

		}

	}

	public static class point implements Comparable<point> {
		long x;
		long y;

		point(long x, long y) {
			this.x = x;
			this.y = y;
		}

		@Override
		public int compareTo(point o) {
			if (o.x < x)
				return 1;
			else if (o.x > x)
				return -1;
			if (o.y < y)
				return 1;
			else
				return 0;
		}
	}

	public static int ch(long y) {
		int r = Long.bitCount(y);
		return r;
	}

	public static int gcd(int x, int y) {
		if (y == 0)
			return x;

		return gcd(y, x % y);
	}

	public static int min[];
	public static int max[];

	public static void build(int s, int e, int p, int a[]) {
		if (s == e) {
			min[p] = a[s];
			max[p] = a[s];
			return;
		}

		int mid = (s + e) / 2;
		build(s, mid, p * 2, a);
		build(mid + 1, e, p * 2 + 1, a);
		min[p] = Math.min(min[p * 2], min[p * 2 + 1]);
		max[p] = Math.max(max[p * 2], max[p * 2 + 1]);
	}

	public static int getMin(int s, int e, int p, int from, int to) {
		if (s > to || e < from)
			return Integer.MAX_VALUE;
		if (s >= from && e <= to)
			return min[p];
		int mid = (s + e) / 2;

		int a = getMin(s, mid, p * 2, from, to);
		int b = getMin(mid + 1, e, p * 2 + 1, from, to);
		return Math.min(a, b);

	}

	public static int getMax(int s, int e, int p, int from, int to) {
		if (s > to || e < from)
			return Integer.MIN_VALUE;
		if (s >= from && e <= to)
			return max[p];
		int mid = (s + e) / 2;

		int a = getMax(s, mid, p * 2, from, to);
		int b = getMax(mid + 1, e, p * 2 + 1, from, to);
		return Math.max(a, b);

	}

	public static void main(String[] args) throws IOException {
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		StringBuilder qq = new StringBuilder();
		PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out));
		String y1[] = in.readLine().split(" ");
		long x = Long.parseLong(y1[0]);
		long y = Long.parseLong(y1[1]);
		long m = Long.parseLong(y1[2]);
		if (x >= m || y >= m) {
			System.out.println(0);
			return;
		}
		long max = Math.max(x, y);
		long min = Math.min(x, y);
		if (max <= 0) {
			System.out.println(-1);
			return;
		} else if (x + y < 0) {
			long ans = 0;
			long r = -1 * min;
			long div = r / max;
			ans += div;
			r = r - div * max;
			min = 0;
			if (r != 0) {
				min = max - r;
				ans++;
			}

			long one = max + min;
			if (one >= m) {
				System.out.println(ans + 1);
				return;
			}
			long two = one + max;
			if (two >= m) {
				System.out.println(ans + 2);
				return;
			}
			ans += 2;

			while (true) {
				long three = one + two;
				ans++;
				if (three >= m) {
					System.out.println(ans);
					return;
				}

				one = two;
				two = three;
			}

		} else {
			long ans = 0;
			long one = Math.max(max, x + y);
			if (one >= m) {
				System.out.println(1);
				return;
			}
			long two = x + y + max;
			if (two >= m) {
				System.out.println(2);
				return;
			}
			ans = 2;

			while (true) {
				long three = one + two;
				ans++;
				if (three >= m) {
					System.out.println(ans);
					return;
				}
				one = two;
				two = three;
			}

		}

	}
}