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.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.FileNotFoundException;
import java.util.StringTokenizer;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Reader in = new Reader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        TaskA solver = new TaskA();
        solver.solve(1, in, out);
        out.close();
    }

    static class TaskA {
        public void solve(int testNumber, Reader in, PrintWriter out) {

            long x = in.nextLong();
            long y = in.nextLong();
            long m = in.nextLong();
            if (x >= m || y >= m) {
                out.println(0);
                out.flush();
                return;
            }
            if (x >= 0 && y >= 0 && m < Math.min(x, y)) {
                out.println(-1);
                out.flush();
                return;
            }
            if (x <= 0 && y <= 0 && m > Math.max(x, y)) {
                out.println(-1);
                out.flush();
                return;
            }
            if (m < 0) {
                m = -m;
                x = -x;
                y = -y;
            }
            long c = 0;
            while (x < m && y < m) {

                if (x > y) {
                    long z = x;
                    x = y;
                    y = z;
                }
                // System.out.println(x+" "+y);
                if (x < y) {

                    if (x + y < y) {
                        long temp = y - x;

                        temp = temp / y;

                        //System.out.println(temp);
                        if (temp > 1) {
                            x += y * (temp);
                            c += temp;
                        } else {
                            x = x + y;
                            c++;
                        }
                    } else {
                        x = x + y;
                        c++;
                    }
                } else {
                    x = x + y;
                    c++;
                }


            }
            out.println(c);
            out.flush();
        }

    }

    static class Reader {
        BufferedReader r;
        StringTokenizer str;

        Reader() {
            r = new BufferedReader(new InputStreamReader(System.in));
        }

        public Reader(InputStream in) {
            r = new BufferedReader(new InputStreamReader(in));
        }

        Reader(String fileName) throws FileNotFoundException {
            r = new BufferedReader(new FileReader(fileName));
        }

        public String getLine() {
            try {
                return r.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return null;
        }

        public String next() {
            if (str == null || !str.hasMoreTokens()) {
                str = new StringTokenizer(getLine());
            }
            return str.nextToken();
        }

        public long nextLong() {
            return Long.parseLong(next());
        }

    }
}

