You are given an integer number n. The following algorithm is applied to it:

  1. if n = 0, then end algorithm; 
  2. find the smallest prime divisor d of n; 
  3. subtract d from n and go to step 1. 



Determine the number of subtrations the algorithm will make.

Input

The only line contains a single integer n (2 ≤ n ≤ 10^{10}).

Output

Print a single integer — the number of subtractions the algorithm will make.

Examples

Input


5


Output


1


Input


4


Output


2

Note

In the first example 5 is the smallest prime divisor, thus it gets subtracted right away to make a 0.

In the second example 2 is the smallest prime divisor at both steps.
//Divisor Subtraction
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;
import java.util.StringTokenizer;
public class DivisorSubtraction
{
	public static void main(String args[]) throws IOException
	{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		long n = Long.parseLong(br.readLine());
		long count = 0;
		while(n != 0){
			if(n%2 == 0){
				count += (long)n/2;
				break;
			}
			else{
				long d = lowestDivisor(n);
				n -= (long)d;
				count++;
			}
		}
		System.out.println(count);
	}
	static long lowestDivisor(long n)
	{
		for(int i = 3; (long)i*i <= n; i += 2){
			if(n%i == 0)
				return i;
		}
		return n;
	}
}