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.*;

public class Main {
    static void zap() throws IOException {
        long x, y, m;
        x = nextLong();
        y = nextLong();
        m = nextLong();
        if(x >= m || y >= m)
        {
            out.println("0");
            return;
        }
        if(x + y <= x && x + y <= y)
        {
            out.println("-1");
            return;
        }
        if(x > y)
            x = y + x - (y = x);
        long offset = 0;
        if(x < 0)
        {
            offset = (long)Math.ceil((-x)/(double)y);
            x = x + offset * y;
        }
        if(x > y)
            x = y + x - (y = x);
        while(y < m)
        {
            x = x + y;
            x = y + x - (y = x);
            offset++;
        }
        out.println(offset);
    }

    static BufferedReader br;
    static StringTokenizer st;
    static PrintWriter out;

    public static void main(String[] args) throws IOException {
        InputStream input = System.in;
        br = new BufferedReader(new InputStreamReader(input));
        out = new PrintWriter(System.out);
        zap();
        out.close();
    }

    static long nextLong() throws IOException {
        return Long.parseLong(nextToken());
    }

    static double nextDouble() throws IOException {
        return Double.parseDouble(nextToken());
    }

    static int nextInt() throws IOException {
        return Integer.parseInt(nextToken());
    }

    static String nextToken() throws IOException {
        while (st == null || !st.hasMoreTokens()) {
            String line = br.readLine();
            if (line == null) {
                return null;
            }
            st = new StringTokenizer(line);
        }
        return st.nextToken();
    }
}