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 divisorSubtraction{
    public static void main (String args []){
        Scanner sc = new Scanner (System.in); 
        long n = sc.nextLong();
        n -= getDivisors(n).get(1); 
        long counter = n/2; 
        counter++; 
        System.out.println(counter); 
    }

    public static ArrayList<Long> getDivisors (long num){
        ArrayList<Long> divs = new ArrayList <Long>(); 
        for(long i = 1; i * i <= num; i++){
            if(i * i == num){
                divs.add(i); 
            }
            else if (num%i == 0){
                divs.add(i); 
                divs.add(num/i); 
            }
        }
        Collections.sort(divs); 
        return divs;  
    }
}  