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.*;
public class GFG {
	public static void main (String[] args) {
		Scanner sc=new Scanner(System.in);
	//	for(int m=1;m<=79;m++){
		long n=sc.nextLong();int h=0,j=0;
		if(n%2==0){
		System.out.println(n/2);h=1;}
		int flag=0;
		if(isPrime(n)==true&&n!=2){
		System.out.println(1);j=1;}
		
		if(h==0&&j==0){
	    long k=0;
	    for(long i=2;i<=n/2;i++)
	    {
	        if(n%i==0&&isPrime(i)==true){
	        k=i;break;}
	    }
//System.out.println(k);
	   if((n-k)%2==0)
	    System.out.println(1+(n-k)/2);
	}}
	public static boolean isPrime(long n)
	{
	    int flag=0;
	    for(int i=2;i<=Math.sqrt(n);i++)
	    {
	        if(n%i==0){flag=1;break;}
	    }
	    if(flag==0)
	    return true;
	    else
	    return false;
	}
}
