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.ArrayList;
import java.util.List;
import java.util.Scanner;

public class Divisor1076B {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long k = sc.nextLong();
        int n = 100001;
        boolean prime[] = new boolean[n+1];
        List<Integer> lis = new ArrayList<>();
        for(int i=0;i<n;i++)
            prime[i] = true;

        for(int p = 2; p*p <=n; p++)
        {
            // If prime[p] is not changed, then it is a prime
            if(prime[p])
            {
                // Update all multiples of p
                for(int i = p*2; i <= n; i += p)
                    prime[i] = false;
            }
        }

        // Prlong all prime numbers
        for(int i = 2; i <= n; i++)
        {
            if(prime[i])
                lis.add(i);
        }
        long count = 0;
        while(k > 0) {
            long temp = k;
            for(int i = 0;i<lis.size() && lis.get(i) <= Math.sqrt(k);i++) {
                if(temp%lis.get(i) == 0) {
                    if(lis.get(i) == 2) {
                        long cur = temp/2;
                        temp = temp - cur*2;
                        count+=cur;

                    } else {
                        temp = temp - lis.get(i);
                        count++;

                    }
                    break;
                }
            }
            if(temp == k) {
                count++;
                System.out.println(count);
                return;
            } else {
                k = temp;
            }
        }
        System.out.println(count);
    }
}
