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.BufferedWriter;
import java.io.File;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.util.Scanner;

public class B1076 {

	public static void main(String[] args) throws IOException{
		Scanner scanner = new Scanner(System.in);
		BufferedWriter log = new BufferedWriter(new OutputStreamWriter(System.out));
		long num = scanner.nextLong();
		long result = 0;
		for(long i = 2; i < Math.sqrt(num) + 1; i++) {
			if(num % i == 0) {
				result++;
				num -= i;
				break;
			}
		}
		
		if(result == 0) {
			result = 1;
			num = 0;
		}
		
		result += num/2l;
		
		log.write("" + result);
		log.flush();

	}
}