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.StringTokenizer;

/**
 * @author kperikov
 */
public class Main implements Runnable {

    PrintWriter out;
    BufferedReader br;
    StringTokenizer st;

    public static void main(String[] args) throws IOException {
        new Thread(new Main()).start();
    }

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

    public int nextInt() throws IOException {
        return Integer.parseInt(next());
    }

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

    public void run() {
        try {
            br = new BufferedReader(new InputStreamReader(System.in));
            out = new PrintWriter(new BufferedOutputStream(System.out));
            solve();
            out.close();
        } catch (IOException e) {
            throw new IllegalStateException(e);
        }
    }

    public void solve() throws IOException {
        long x = nextLong();
        long y = nextLong();
        long m = nextLong();
        if (x >= m || y >= m) {
            out.println(0);
            return;
        }
        if (x <= 0 && y <= 0) {
            out.println(-1);
            return;
        }
        long count = 0;
        if (x < 0 || y < 0) {
            if (x < 0) {
                long t = (Math.abs(x) / y);
                x = x + t * y;
                count += t;
                while (x < m && y < m) {
                    if (x < y) {
                        x = x + y;
                    } else {
                        y = x + y;
                    }
                    ++count;
                }
                out.println(count);
            } else if (y < 0) {
                long t = (Math.abs(y) / x);
                y = y + t * x;
                count += t;
                while (x < m && y < m) {
                    if (x < y) {
                        x = x + y;
                    } else {
                        y = x + y;
                    }
                    ++count;
                }
                out.println(count);
            }

        } else {
            while (x < m && y < m) {
                if (x < y) {
                    x = x + y;
                } else {
                    y = x + y;
                }
                ++count;
            }
            out.println(count);
        }

    }

    class Pair implements Comparable {
        int f;
        int s;

        Pair(int f, int s) {
            this.f = f;
            this.s = s;
        }

        @Override
        public boolean equals(Object o) {
            if (this == o) return true;
            if (o == null || getClass() != o.getClass()) return false;

            Pair pair = (Pair) o;

            if (f != pair.f) return false;
            if (s != pair.s) return false;

            return true;
        }

        @Override
        public int hashCode() {
            int result = f;
            result = 31 * result + s;
            return result;
        }

        @Override
        public int compareTo(Object o) {
            Pair p = (Pair) o;
            if (p.f >= this.f) {
                return -1;
            }
            if (p.f == this.f) {
                return 0;
            }
            return 1;
        }
    }
}
