// Arup Guha
// 6/16/2023
// Showing an example of using Codeforces...
// https://codeforces.com/problemset/problem/486/A

using namespace std;
#include <iostream>

int main() {

    long long n;
    cin >> n;

    // Even case is 1+1...+1
    if (n%2 == 0)
        cout << n/2 << endl;

    // Odd case is -1-1...
    else
        cout << -(n+1)/2 << endl;

    return 0;
}