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.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.StringTokenizer;


public class PerfectPair {

	
	static IR in = new IR(System.in);
	public static void main(String[]args)throws Throwable
	{
		long a,b,m;
		a = in.ll(); b = in.ll(); m = in.ll();
		
	
		
		if(a > b)
		{
			long tmp = b;
			b = a;
			a = tmp;
		}
		
		if(a >= m || b >= m)
		{
			System.out.println("0");
			return;
		}
		
		if(a <= 0 && b == 0)
		{
			System.out.println("-1");
			return;
		}
		if(a < 0 && b < 0)
		{
			System.out.println("-1");
			return;
		}
		long steps = 0;
		if(a < 0 && b > 0)
		{
			steps += (Math.abs(a)) / b;
			if(Math.abs(a) % b != 0) ++steps;
			a = a + b * steps;
		}
		
		
		while((m > a ) && (m > b))
		{
			if(a > b) b = a + b;
			else a = a + b;
			++steps;
		}
		
		
		System.out.println(steps);
		
	}
	
	static	class IR {
		public BufferedReader reader;
		public StringTokenizer tokenizer;

		public IR(InputStream stream) {
			reader = new BufferedReader(new InputStreamReader(stream), 32768);
			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 j() {
			return Integer.parseInt(next());
		}
		public long ll(){
			return Long.parseLong(next());
		}


	}
}
