题解 | #牛牛学数列#

import java.util.Scanner;

public class Main{
    public static void main(String[] args){
        Scanner scan = new Scanner(System.in);
        int a = scan.nextInt();
        //两两相加的负一，n为偶数则有(1/2)n个-1
        if(a % 2 == 0){
            a = a / 2 * (-1);
        }else {
            //n为奇数找到规律(1/2)n个-1 + n本身
            a = a + a / 2 * (-1);
        }
        System.out.println(a);
    }
}