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.
#include <bits/stdc++.h>
using namespace std;
int main() {
  long long a, k, m, b, x, y, n;
  string s;
  int i = 2;
  cin >> n;
  a = n;
  while (n > 0) {
    if (n % 10 == 0) {
      b = n;
      break;
    }
    if (n % i == 0 && n - i > 0) {
      n = n - i;
    } else if (n % i == 0 && n - i == 0) {
      b = n;
      break;
    } else
      i++;
  }
  if (a == b && n % 10 != 0)
    cout << 1;
  else if (a == b && n % 10 == 0)
    cout << 2;
  else
    cout << b;
}
