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.util.*;
import java.io.*;
public class Solution{
	static class Pair{
		int x, y, z;
		Pair(int a, int b, int c){
			x = a;
			y = b;
			z = c;
		}
		public String toString() {
			return String.valueOf(x)+" "+String.valueOf(y)+" "+String.valueOf(z);
		}
	}
	static int[] movex;
	static int[] movey;
	static Map<Character, Integer> map;
	public static void main (String[] args) throws java.lang.Exception
	{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		long n = Long.parseLong(br.readLine());
		int q = (int)Math.sqrt(n);
		if((n&1)==0) {
			System.out.println(n>>1);
		}
		else {
			Long prev = n;
			for(int i = 3;i<=q;i++) {
				if(n%i==0) {
					n-=i;
					break;
				}
			}
			if(prev==n) {
				System.out.println(1);
			}
			else {
				System.out.println(1+(n>>1));
			}
		}
	}
}