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.io.*;
import java.math.BigInteger;
import java.util.*;
                                 
public class Main {
                             
    static Scanner in;
         
//  static StreamTokenizer in;
//  static int nextInt() throws IOException {
//      in.nextToken();
//      return (int)in.nval;    
//  }
    static Random rand = new Random();
    static long gcd(long a, long c) {
        BigInteger q = BigInteger.valueOf(a);
        BigInteger w = BigInteger.valueOf(c);
        q = q.gcd(w);
        return q.longValue();
    }

    public static void main(String args[]) throws IOException {
    	
//      in = new StreamTokenizer(new BufferedReader(new InputStreamReader(System.in)));
        in = new Scanner(System.in);         
        PrintWriter out = new PrintWriter(System.out);
        long n = in.nextLong();
        if(n%2==0) {
        	System.out.println(n/2);
        	return;
        }else {
        	int ans = 1;
        	for(int i =2;i<Math.sqrt(n)+100;i++){
        		if(n%i == 0) {
        			ans = i;
        			break;
        		}
        	}
        	n-=ans;
        	if(ans == 1) System.out.println(1);
        	else System.out.println(n/2+1);
        }
    }
}
                                 
class Pair implements Comparable{
	int a;
    int b;
    public Pair() {
        this.a = 0;
        this.b = 0;
    }
    public Pair(int a, int b) {
        this.a = a;
        this.b = b;
    }
    public int compareTo(Object arg0) {
        if(Integer.compare(this.a, ((Pair) arg0).a) == 0) return Integer.compare(this.b, ((Pair) arg0).b);
            return Integer.compare(this.a, ((Pair) arg0).a);
    }
}