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.util.Arrays;
import java.util.Scanner;

public class Main {

    public static void bubbleSort(int[] A, int n) {
        for (int i = 0; i < n - 1; i++) {
            for (int j = i + 1; j < n; j++) {
                if (A[i] > A[j]) {

                    int temp = A[i];
                    A[i] = A[j];
                    A[j] = temp;
                }
            }
        }
    }

    public static int binarySearch(int[] A, int n, int x) {
        int low = 0, high = n;

        while (low != high) {
            int mid = low + (high - low) / 2;
            // if(x==A[mid]) return mid;
            if (x >= A[mid]) low = mid + 1;
            else high = mid;
        }
        return high;
    }

    public static void main(String args[]) {

        Scanner in = new Scanner(System.in);

        long x, y, m,counter=0;

        x = in.nextLong();
        y = in.nextLong();
        m = in.nextLong();

        if((x<=0&&y<=0&&m>0)||(x<m&&y<m&&m<0)) {
            System.out.println(-1);
            return;
        }
        else if(x>=m||y>=m)
        {
            System.out.println(0);
            return;
        }

        if(y<0)
        {
            long n = (-y)/x;
            counter+=n;
            y+=n*x;
        }

        else if(x<0)
        {
            long n = (-x)/y;
            counter+=n;
            x+=n*y;
        }
        while(x<m&&y<m) {
         if (x < y){
                    x += y;
                    counter++;
                }
            else
                {
                    y += x;
                    counter++;
                }
        }

        System.out.println(counter);



    }
}
