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.util.*;
import java.io.*;

public class Main {

	BufferedReader in;
	StringTokenizer str = null;
	PrintWriter out;
	
	private String next() throws Exception{
		if (str == null || !str.hasMoreElements())
			str = new StringTokenizer(in.readLine());
		return str.nextToken();
	}
	
	private int nextInt() throws Exception{
		return Integer.parseInt(next());
	}
	
	private long nextLong() throws Exception{
		return Long.parseLong(next());
	}
	
	private double nextDouble() throws Exception{
		return Double.parseDouble(next());
	}
	
	public void run() throws Exception{
		in =  new BufferedReader(new InputStreamReader(System.in));
		out = new PrintWriter(System.out);
		long x = nextLong();
		long y = nextLong();
		long m = nextLong();
		if (x >= m || y >= m) {
			out.println(0);
			out.close();
			return;
		}

		if (x + y <= Math.min(x, y)) {
			out.println(-1);
			out.close();
			return;
		}
		if (x > y) {
			long c = x;
			x = y;
			y = c;
		}
		
		long t = 0;
		if (x < 0){
			x = -x;
			if (x % y == 0) {
				t = x/y;
				x = 0;
			}else{
				t = x/y + 1;
				if (x > y) {
					//x = x - y*(x/y);
					x = y - x%y;
				}else{
					x = y - x;
				}
			}
		}
		
		//System.out.println(x + " " + y);
		while(Math.max(x, y) < m){
			long a[] = new long[]{x, y, x + y};
			Arrays.sort(a);
			x = a[1];
			y = a[2];
			t++;
		}
		out.println(t);
		out.close();
	}
		
	public static void main(String[] args) throws Exception{
		new Main().run();
	}
}
