#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<int,int>
#define fi first
#define se second
#define pb push_back
#define sz size()
#define faster() ios_base::sync_with_stdio(0); cin.tie(NULL); cout.tie(NULL);
#define vi vector<int>
#define vll vector<ll>
#define vs vector<string>
#define PI 3.141592653589793238
//C:\Users\Public\cpp_learning\input.txt
int main()
{
    int n; cin >> n;
    ll s = 0;
    for (ll i=1; i<=n; i++)
    {
        s += (pow(-1, i+1) * i);
    }
    cout << s;
    return 0;
}