#include <bits/stdc++.h>   using namespace std;   const int maxn = 1000000 + 10;   char b[maxn];   int a[maxn];   int ccc[20];   int main() {     long long n;     long long sum = 0;     cin >> n;     if (n % 2 == 0)       sum = n / 2;     else       sum = (-n - 1) / 2;     cout << sum << endl;     return 0;   }   