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 MyClass {
    public static void main(String args[]) {
        Scanner scan = new Scanner(System.in);
        long x = scan.nextLong();
        if(isPrime(x)){
            System.out.println(1);
            return;
        }
        int count = 0;
        if(x % 2 == 1) {
            x -= findPrime(x);
            count++;
        }
        System.out.println(count + (x/2));
    }
    
     static boolean isPrime(long n) 
    { 
        if (n <= 1) return false; 
        if (n <= 3) return true; 
      
        if (n % 2 == 0 || n % 3 == 0) return false; 
      
        for (long i = 5; i * i <= n; i = i + 6) 
            if (n % i == 0 || n % (i + 2) == 0) 
            return false; 
      
        return true; 
    }
    
    static long findPrime(long n) {
        for(long i = 1; i < n; i++) {
                if(n % i == 0 && isPrime(i)) return i;
        }
        return -1;
    }
}
