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.*;
import java.io.*;

public class Solution{
	static PrintWriter out=new PrintWriter(System.out);
	public static void main (String[] args) throws IOException{
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		
		String[] temp=br.readLine().trim().split(" ");
		
		long n=Long.parseLong(temp[0]);
		out.println(numSubtractions(n));
		
		out.flush();
		out.close();
	}
	public static long numSubtractions(long n)
	{
	    if(isPrime(n)){
	        return 1;
	    }
	    if(n%2==0){
	        return n/2;
	    }
	    for(long i=2;i<=Math.sqrt(n);i++){
	        if(n%i==0){
	            long d1=i;
	            long d2=n/i;
	            if(isPrime(d1))
	            {
	                return 1+(n-d1)/2;
	            }
	            else if(isPrime(d2)){
	                return 1+(n-d2)/2;
	            }
	        }
	    }
	    return 0;
	}
	public static boolean isPrime(long x){
	    for(long i=2;i<=Math.sqrt(x);i++){
	        if(x%i==0){
	            return false;
	        }
	    }
	    return true;
	}
}