#include <bits/stdc++.h>
using namespace std;
const double pi = acos(-1);
template <class T>
inline bool read(T &x) {
  x = 0;
  register char c = getchar();
  register bool f = 0;
  while (!isdigit(c)) {
    if (c == EOF) return false;
    f ^= c == '-', c = getchar();
  }
  while (isdigit(c)) x = (x << 3) + (x << 1) + (c ^ 48), c = getchar();
  if (f) x = -x;
  return true;
}
template <class T>
inline void print(T x) {
  if (x < 0) putchar('-'), x = -x;
  if (x > 9) print(x / 10);
  putchar(x % 10 ^ 48);
}
template <class T>
inline void print(T x, char c) {
  print(x), putchar(c);
}
template <class T, class... S>
inline bool read(T &x, S &...y) {
  return read(x) && read(y...);
}
long long n;
string ans;
int main() {
  read(n);
  if (n & 1)
    print(-n / 2 - 1, '\n');
  else
    print(n / 2, '\n');
  return 0;
}
