import java.util.*;
public class Main
{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int ne,no;
		long sum = 0;
		if(n%2==0) {
		    ne = n/2;
		    no = n/2;
		     sum = (long)ne;
		}else{
		    ne = n/2;
		    no = (n/2)+1;
		    sum = -1*((long)ne+1);
		}
		
		System.out.println(sum);
		
	}
}