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.Scanner;

public class divisorsubtraction {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long n = sc.nextLong();
		sc.close();
		long subs = 0;
		while(n > 0) {
			if(n % 2 == 0) {
				subs+= (n/2);
				break;
			}
			long num = isPrime(n);
			if(num == n) {
				subs++;
				break;
			}
			else {
				n -= num;
				subs++;
			}
		}
		System.out.println(subs);
	}
	
	public static long isPrime(long n) {
		for(int i = 3; i <= Math.sqrt(n); i+= 2) {
			if(n % i == 0) {
				return i;
			}
		}
		return n;
	}
}