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 C {
	
	class InputReader {

		public BufferedReader reader;
		public StringTokenizer tokenizer;

		public InputReader(InputStream stream) {
			reader = new BufferedReader(new InputStreamReader(stream));
			tokenizer = null;
		}
	
		public InputReader() throws FileNotFoundException{
			reader = new BufferedReader(new FileReader("d:/input.txt"));
			tokenizer = null;
		}

		public String next() {
			while (tokenizer == null || !tokenizer.hasMoreTokens()) {
				try {
					tokenizer = new StringTokenizer(reader.readLine());
				} catch (IOException e) {
					throw new RuntimeException(e);
				}
			}
			return tokenizer.nextToken();
		}

		public int nextInt() {
			return Integer.parseInt(next());
		}
		
		public long nextLong(){
			return Long.parseLong(next());
		}
		
	}
	
	public void run(){
		
		InputReader reader = new InputReader(System.in);
		long x = reader.nextLong() , y = reader.nextLong();
		long m = reader.nextLong();
		long tmp = Math.max(x, y);
		if(m <= tmp){
			System.out.println(0);
		}
		else{
			if(x <=0 && y <= 0){
				System.out.println(-1);
			}else{
				long cnt = 0;
				long X = Math.min(x, y);
				long Y = Math.max(x, y);
				if(X < 0){
					cnt = (-1*X)/Y;
					X += cnt*Y;
				}
				x = X;
				y = Y;
				while(Math.max(x, y) < m){
					if(x < y){
						x = x + y;
					}else{
						y = x + y;
					}
					cnt ++;
				}
				System.out.println(cnt);
			}
		}
		
	}
	
	public static void main(String[] args) {
		new C().run();
	}

}
