import java.util.*;
public class Main {
    

    public static int gab(int a) {

        int c = a/2; 
        return c;  
    } 
   
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        int b = input.nextInt();
        System.out.println(gab(b)); 
    }
}