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.BufferedReader;
import java.io.InputStreamReader;

public class div {
	public static void main(String args[]) throws Exception{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		long n = Long.parseLong(br.readLine());
		if(n<2) System.out.println(0);
		long count=0;
		while(n>0) {
			if(n%2==0) {
				count= (n/2);
				break;
			}
			else {
				int i = 3;
				while(n%i!=0) {
					i+=2;
				}
				n=n-i;
			}
			count++;
		}
		System.out.println(count);
	}
	

}
