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 Main {
    static long n;
    static int[] arr;
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        n = sc.nextLong();
        arr = new int[10000001];
        getPrime(10000000);
        long result = 0;
        for(int i=0;i<list.size();i++){
            if(n%list.get(i)==0){
                result = n/list.get(i);
                n -= list.get(i);
                break;
            }
        }
        System.out.println(result);
    }

    static List<Integer> list = new ArrayList<>();
    private static void getPrime(long n){
        for(int i=2;i<=n;i++){
            if(arr[i]==0) list.add(i);
            else continue;
            for(long j=2;i*j<=n;j++){
                arr[(int)(i*j)] = 1;
            }
        }
    }
}