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;

public class PerfectPair {
    public static void main(String... args) throws IOException {
        InputStreamReader isr = new InputStreamReader(System.in);
        BufferedReader br = new BufferedReader(isr);
        String line = br.readLine();
        String[] tab = line.split(" ");
        long x = Long.parseLong(tab[0]);
        long y = Long.parseLong(tab[1]);
        long m = Long.parseLong(tab[2]);

        long counter = 0L;
        double biggest = Math.pow(10, 18);
        if (x>y){
            long tmp = x;
            x = y;
            y = tmp;
        }
        if (x>=m || y>=m){
            System.out.println(0);
            return;
        }
        if (((x <= 0 && y <= 0) || (x + y < x && x + y < y)) && x < m && y < m) {
            counter = -1L;
        } else {
            if (x<=0){
                counter = (Math.abs(x)+y)/y;
                x+=((Math.abs(x)+y)/y)*y;
            }
            while (x <= biggest && y <= biggest && x < m && y < m) {
                if (x < y) {
                    x = x + y;
                } else {
                    y = x + y;
                }
                counter++;
            }
        }

        if (x < m && y < m) {
            counter = -1L;
        }

        System.out.println(counter);

    }
}