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 a{
	
	public static void main(String[] args) {
		Scanner in=new Scanner(System.in);
		long n=in.nextLong();


		long count=0;

		while(n!=0){
				
			long lpd=0;
			boolean found=false;

			long x=n;
			for(long j=2;j<=Math.sqrt(x);j++){
					
				while(x%j==0){
				
					if(!found)
						lpd=j;
					
					x=x/j;
				}
			
			}
			if(x>1)
				lpd=x;

			//System.out.println(lpd);

			n=n-lpd;
			count++;
		
		}
		System.out.println(count);
		
		
	}
}