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

public class test {
	static int MAX = 1000001;
	public static void main(String[] argvs) throws Exception{
		FastScanner scan = new FastScanner(System.in);
		long x = scan.nextLong();
		long y = scan.nextLong();
		long m = scan.nextLong();
		
		if(x <= 0 && y <= 0) {
			if(Math.max(x, y) < m){
				System.out.println(-1);
			} else
				System.out.println(0);
			return;
		}
		if(Math.max(x, y) >= m){
			System.out.println(0);
			return;
		}
		long cnt = 0;
		if(x > y){
			long temp = x;
			x = y;
			y = temp;
		}
		if(x < 0 && y > 0){
			cnt += (x * -1) / y;
			x += cnt * y;
		}
		while(x < m && y < m){
			if(x < y) x = x + y;
			else y = x + y;
			++cnt;
		}
		System.out.println(cnt);
	}
	
	static class FastScanner {
		BufferedReader br;
		StringTokenizer st;

		public FastScanner(InputStream in) throws Exception {
			br = new BufferedReader(new InputStreamReader(in));
			st = new StringTokenizer(br.readLine().trim());
		}

		public int numTokens() throws Exception {
			if (!st.hasMoreTokens()) {
				st = new StringTokenizer(br.readLine().trim());
				return numTokens();
			}
			return st.countTokens();
		}

		public boolean hasNext() throws Exception {
			if (!st.hasMoreTokens()) {
				st = new StringTokenizer(br.readLine().trim());
				return hasNext();
			}
			return true;
		}

		public String next() throws Exception {
			if (!st.hasMoreTokens()) {
				st = new StringTokenizer(br.readLine().trim());
				return next();
			}
			return st.nextToken();
		}

		public double nextDouble() throws Exception {
			return Double.parseDouble(next());
		}

		public float nextFloat() throws Exception {
			return Float.parseFloat(next());
		}

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

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

		public String nextLine() throws Exception {
			return br.readLine();
		}
	}
}