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.*;

public final class Solution {
  public static void main(String[] args) {
    Scanner input = new Scanner(System.in);
    long n = input.nextLong();
    if ((n % 2)== 0) {
      System.out.println(n/2);
      return;
    }
    boolean isPrime = true;
    long prime = 1;
    for (long i = 2; i <= (long)Math.sqrt(n); i++) {
      if ((n % i) == 0) {
        isPrime = false;
        prime = i;
        break;
      }
    }
    if (isPrime) {
      System.out.println("1");
    } else {
      System.out.println((n - prime)/2 + 1);
    }
  }
}
