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

public class B {

	public static void main(String[] args)throws IOException {
		
		BufferedReader ob = new BufferedReader(new InputStreamReader(System.in));
		StringBuffer sb=new StringBuffer();
		
		long n=Long.parseLong(ob.readLine());
		
		long count=0;
		long pf=primeFactors(n);
		if((pf&1)!=0)
		{
			count++;
			n-=pf;
		}
		count+=(n/2);
		System.out.println(count);
		
	}
	static long primeFactors(long n) 
	{
		
		for (int i = 2; i <= Math.sqrt(n); i++) {
			if (n % i == 0) 
			{
				return i;
			}
		}
		return n;

	}
}