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.*;
import java.io.*;

public class taskC {
    
    void solution(Input in, PrintWriter out) throws IOException {
        long x = in.nextLong(), y = in.nextLong(), m = in.nextLong();
        long ans = 0;
        if (x >= m || y >= m)
            out.println("0");        
        else if (x <= 0 && y <= 0)
            out.println("-1");
        else {            
            long tx = Math.max(x, y);
            long ty = Math.min(x, y);
            if (ty < 0) {
                ans += -ty / tx + 1;
                ty += ans * tx;
            }
            x = tx; y = ty;
            while (x < m) {
                tx = x + y;
                ty = Math.max(x, y);
                x = Math.max(tx, ty);
                y = Math.min(tx, ty);
                ans++;
            }
            out.println(ans);
        }
    }
    
    public static void main(String[] args) throws IOException {
        Input in = new Input(new BufferedReader(new InputStreamReader(System.in)));
        PrintWriter out = new PrintWriter(System.out);
        (new taskC()).solution(in, out);
        out.close();
    }
    
    static class Input {
    
        BufferedReader in;
        StringTokenizer st;
        
        public Input(BufferedReader in) {
            this.in = in;
        }
        
        public String next() throws IOException {
            while (st == null || !st.hasMoreTokens())
                st = new StringTokenizer(in.readLine());            
            return st.nextToken();
        }
        
        public int nextInt() throws IOException {
            return Integer.parseInt(next());
        }
        
        public long nextLong() throws IOException {
            return Long.parseLong(next());
        }
        
        public double nextDouble() throws IOException {
            return Double.parseDouble(next());
        }
    }
}