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.StreamTokenizer;
import java.io.InputStreamReader;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.io.Reader;
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;
		TokenizerReader in = new TokenizerReader(inputStream);
		PrintWriter out = new PrintWriter(outputStream);
		TaskC solver = new TaskC();
		solver.solve(1, in, out);
		out.close();
	}
}

class TaskC {
    public void solve(@SuppressWarnings("UnusedParameters") int testNumber, TokenizerReader in, PrintWriter out) {
        long x = in.nextLong(), y = in.nextLong(), m = in.nextLong();
        if (x > y) {
            long t = x;
            x = y;
            y = t;
        }
        if (y >= m) {
            out.println(0);
            return;
        }
        if (y <= 0) {
            out.println(-1);
            return;
        }
        long res = 0;
        if (x <= 0) {
            res = Math.abs(x) / y + 1;
            x += res * y;
        }
        while (y < m) {
            long s = x+y;
            x = y;
            y = s;
            ++res;
        }
        out.println(res);
    }
}

class TokenizerReader extends StreamTokenizer {
    public TokenizerReader(InputStream in) {
        super(new BufferedReader(new InputStreamReader(in)));
        defaultConfig();
    }

    public String nextString() {
        try {
            nextToken();
        } catch (IOException e) {
            throw new RuntimeException("nextString: exception in line " + lineno(), e);
        }
        return sval;
    }

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

    public void defaultConfig() {
        resetSyntax();
        wordChars(33, 126);
        whitespaceChars(0, ' ');
    }

    }

