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.BufferedWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.math.BigInteger;
import java.util.Arrays;
import java.util.StringTokenizer;


public class TaskA implements Runnable {
    
    private long max(long a, long b) {
        return a > b ? a : b;
    }
    
    private void solve() {
        if (a <= 0 && b <= 0) {
            out.println(max(a, b) >= m ? 0 : -1);
        }
        else {
            if (max(a, b) >= m) { out.println(0); return; }        

            long cnt = 0;
            if (a < 0) {
                cnt = -a/b;
                a += cnt*b;
            }
            if (b < 0) {
                cnt = -b/a;
                b += cnt*a;
            }
            while (max(a, b) < m) {
                ++cnt;
                if (a < b) {
                    a += b;
                }
                else {
                    b += a;
                }
            }
            out.println(cnt);
        }
    }
    
    private void readData() {
        a = in.readLong();
        b = in.readLong();
        m = in.readLong();
    }
    
    private long a;
    private long b;
    private long m;
    
    private void begin() {
        in = new InputReader(System.in);
        out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)));
    }
    
    private void end() {
        out.flush();
    }
    
    private InputReader in;
    private PrintWriter out;
    
    @Override
    public void run() {
        begin();
        readData();
        solve();        
        end();
    }

    public static void main(String[] args) {
        new TaskA().run();
    }
    
    private class InputReader {
        
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream));
            tokenizer = null;
        }

        public String next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } 
                catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }
        
        public int readInt() {
            return Integer.parseInt(next());
        }
        
        public long readLong() {
            return Long.parseLong(next());
        }
        
        public String readString() {
            try {
                return reader.readLine();
            } 
            catch (IOException e) {             
                e.printStackTrace();
                throw new RuntimeException(e);
            }
        }
        
    }

}