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.InputStreamReader;
import static java.lang.Math.*;
import java.util.ArrayList;
import java.util.Scanner;
/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

/**
 *
 * @author pttrung
 */
public class C {

    public static long con = 3 * 1000000000000000000L;

    public static void main(String[] args) {
        Scanner in = new Scanner(new InputStreamReader(System.in));
        long x = in.nextLong();
        long y = in.nextLong();
        long m = in.nextLong();

        long result = cal(x, y, m);
        if (result >= con) {
            result = -1;
        }
        System.out.println(result);
    }

    static long cal(long x, long y, long m) {
        // System.out.println(x + " " + y + " " + m);
        if (x >= m || y >= m) {
            return 0;
        }
        if (x <= 0 && y <= 0) {
            return con;
        }
        long step = 0;
        if (x > 0 && y < 0) {
            step = (long) Math.ceil((double) Math.abs(y) / x);
            y += x * step;
        } else if (x < 0 && y > 0) {
            step = (long) Math.ceil((double) Math.abs(x) / y);
            x += y * step;
        }
       // System.out.println(x + " " + y);
        long a = con, b = con;
        if (x < y) {
            a = 1 + step + cal(x + y, y, m);
        } else {
            b = 1 + step + cal(x, x + y, m);
        }
        return Math.min(a, b);


    }

    static void check(Point a, Point b, ArrayList<Point> p, Point[] rec, int index) {
        for (int i = 0; i < 4; i++) {
            int m = (i + index) % 4;
            int j = (i + 1 + index) % 4;
            Point k = intersect(minus(b, a), minus(rec[m], rec[j]), minus(rec[m], a));
            if (k.x >= 0 && k.x <= 1 && k.y >= 0 && k.y <= 1) {
                Point val = new Point(k.x * minus(b, a).x, k.x * minus(b, a).y);
                p.add(add(val, a));
                // System.out.println(a + " " + b + " " + rec[i] + " " + rec[j]);
                // System.out.println(add(val, a));
            }
        }
    }

    static Point intersect(Point a, Point b, Point c) {
        double D = cross(a, b);
        if (D != 0) {
            return new Point(cross(c, b) / D, cross(a, c) / D);
        }
        return null;
    }

    static Point convert(Point a, double angle) {
        double x = a.x * cos(angle) - a.y * sin(angle);
        double y = a.x * sin(angle) + a.y * cos(angle);
        return new Point(x, y);
    }

    static Point minus(Point a, Point b) {
        return new Point(a.x - b.x, a.y - b.y);
    }

    static Point add(Point a, Point b) {
        return new Point(a.x + b.x, a.y + b.y);
    }

    static double cross(Point a, Point b) {
        return a.x * b.y - a.y * b.x;
    }

    static class Point {

        double x, y;

        Point(double x, double y) {
            this.x = x;
            this.y = y;
        }

        @Override
        public String toString() {
            return "Point: " + x + " " + y;
        }
    }
}
