Codeforces_486A

//Codeforces Round 486A
#include <iostream>
using namespace std;
void funkc(long long int n)
{
    if(n%2==0){cout << n/2;}
    else{cout << -(n+1)/2;}
}
int main()
{
    long long int n;
    cin >> n;
    funkc(n);
    return 0;
}