题解 | #牛牛学数列#

#include <stdio.h>

int main() {
    int n;
    scanf("%d",&n);
    int i;
    if(n%2==0)
    {
        printf("%d",-1*n/2);
    }else{
        printf("%d",-1*(n-1)/2+n);
    }
    return 0;
}