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.ArrayList;
import java.util.Collections;
import java.util.List;

public class Task317AA {

    public static void main(String... args) throws NumberFormatException,
            IOException {
        Solution.main(System.in, System.out);
    }

    static class Scanner {

        private final BufferedReader br;
        private String[] cache;
        private int cacheIndex;

        Scanner(InputStream is) {
            br = new BufferedReader(new InputStreamReader(is));
            cache = new String[0];
            cacheIndex = 0;
        }

        int nextInt() throws IOException {
            if (cacheIndex >= cache.length) {
                cache = br.readLine().split(" ");
                cacheIndex = 0;
            }
            return Integer.parseInt(cache[cacheIndex++]);
        }

        long nextLong() throws IOException {
            if (cacheIndex >= cache.length) {
                cache = br.readLine().split(" ");
                cacheIndex = 0;
            }
            return Long.parseLong(cache[cacheIndex++]);
        }

        String next() throws IOException {
            if (cacheIndex >= cache.length) {
                cache = br.readLine().split(" ");
                cacheIndex = 0;
            }
            return cache[cacheIndex++];
        }

        void close() throws IOException {
            br.close();
        }

    }


    static class Solution {


        public static void main(InputStream is, OutputStream os)
                throws NumberFormatException, IOException {
            PrintWriter pw = new PrintWriter(os);
            Scanner sc = new Scanner(is);

            long x = sc.nextLong();
            long y = sc.nextLong();
            long m = sc.nextLong();

            if(x >= m || y >= m){
                pw.println(0);
            } else {
                if(x <= 0 && y <= 0){
                    pw.println(-1);
                }
                else{
                    if(x < y){
                        long tmp = x;
                        x = y;
                        y = tmp;
                    }
                    long retVal = 0;
                    if (y < 0)
                    {
                        long n = (-y) / x + 1;
                        retVal += n;
                        y += x * n;
                    }
                    while (x < m)
                    {
                        y += x;
                        long tmp = x;
                        x = y;
                        y = tmp;
                        retVal += 1;
                    }
                    pw.println(retVal);        
                }
            }

            pw.flush();
            sc.close();
        }
    }

}