#include <iostream>
using namespace std;

int main() {
    int n;
    cin>>n;
    if (n%2==0) {
        cout<<(-1)*(n/2);
    }
    else  cout<<(n+1)/2;
    //1 -1 2 -2 3 -3
    //1  2 3  4 5  6
}   
// 64 位输出请用 printf("%lld")

跟做数学题一样