#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; using ll = long long; using P = pair; constexpr int INF = 1001001001; // constexpr int mod = 1000000007; constexpr int mod = 998244353; template inline bool chmax(T& x, T y){ if(x < y){ x = y; return true; } return false; } template inline bool chmin(T& x, T y){ if(x > y){ x = y; return true; } return false; } int main(){ ios::sync_with_stdio(false); cin.tie(nullptr); int n; cin >> n; if(n == 0){ cout << 0 << endl; return 0; } vector ord(n); int l = 1, r = n, i = 0, j = n - 1; while(l <= r){ if(l == r) ord[i] = l++; else{ if(i % 2 == 0){ ord[i++] = l++; ord[j--] = r--; } else{ ord[j--] = l++; ord[i++] = r--; } } } ll ans = 0; for(int i = 0; i < n; ++i){ ans += (ll)ord[i] * ord[(i + 1) % n]; } cout << ans << endl; return 0; }