`color(#FFFFFFff)(H)color(#E7E7E7ff)(o)color(#CFCFCFff)(r)color(#B7B7B7ff)(i)color(#9F9F9Fff)(z)color(#878787ff)(o)color(#6F6F6Fff)(n)`

#include <iostream>
using namespace std;

int main() {
    int n; cin >> n;
    if (n % 2 == 0) cout << -1 * (n / 2);
    else cout << -1 * ((n - 1)/2) + n;
    return 0;
}

#include<iostream>
using namespace std;
int main(){
    int n;
    cin>>n;
    cout<<(n%2==0?-n/2:-((n-1)/2)+n);
    return 0;
}