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 class MyClass {
    public static void main(String args[]) {
        Scanner scan = new Scanner(System.in);
        long n = scan.nextLong();
        long tmp = n;
        if(n % 2 == 0){
            System.out.println(n/2);
        }
        else{
            Set<Long> set = new TreeSet<>();
            for(long i = 2; i * i <= 1e10 ; i++){
                if(n % i == 0 ){
                    if(i != 2)
                        set.add(i);
                    while(n % i == 0){
                        n /= i;
                    }
                }
            }
            if( n > 1 && n != 2) set.add(n);
            Iterator<Long> iter = set.iterator();
            long sm = iter.next();
            System.out.println(1 + ((tmp - sm) / 2));
        }
    }
}
