#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; //#define int long long typedef long long ll; typedef unsigned long long ul; typedef unsigned int ui; const ll mod = 1000000007; const ll INF = (1e+18) + 7; typedef pairP; #define stop char nyaa;cin>>nyaa; #define rep(i,n) for(int i=0;i=0;i--) #define Rep(i,sta,n) for(int i=sta;i=1;i--) #define Rep1(i,sta,n) for(int i=sta;i<=n;i++) #define all(v) (v).begin(),(v).end() typedef pair LP; typedef long double ld; typedef pair LDP; const ld eps = 1e-6; const ld pi = acos(-1.0); //typedef vector> mat; typedef vector vec; ll mod_pow(ll a, ll n) { ll res = 1; while (n) { if (n & 1)res = res * a%mod; a = a * a%mod; n >>= 1; } return res; } struct modint { ll n; modint() :n(0) { ; } modint(ll m) :n(m) { if (n >= mod)n %= mod; else if (n < 0)n = (n%mod + mod) % mod; } operator int() { return n; } }; bool operator==(modint a, modint b) { return a.n == b.n; } modint operator+=(modint &a, modint b) { a.n += b.n; if (a.n >= mod)a.n -= mod; return a; } modint operator-=(modint &a, modint b) { a.n -= b.n; if (a.n < 0)a.n += mod; return a; } modint operator*=(modint &a, modint b) { a.n = ((ll)a.n*b.n) % mod; return a; } modint operator+(modint a, modint b) { return a += b; } modint operator-(modint a, modint b) { return a -= b; } modint operator*(modint a, modint b) { return a *= b; } modint operator^(modint a, int n) { if (n == 0)return modint(1); modint res = (a*a) ^ (n / 2); if (n % 2)res = res * a; return res; } //ll inv(ll a, ll p) { // return (a == 1 ? 1 : (1 - p * inv(p%a, a)) / a + p); //} //modint operator/(modint a, modint b) { return a * modint(inv(b, mod)); } int dx[4] = { 1,0,-1,0 }; int dy[4] = { 0,1,0,-1 }; int trans(string &s) { int res = 0; rep(i, s.size()) { if (s[i] == ':') { string le = s.substr(0, i); string ri = s.substr(i + 1, s.size() - i - 1); res = stoi(le) * 60 + stoi(ri); break; } } return res; } void solve() { int n; cin >> n; ll ans = 0; rep1(i, n) { ans = max(ans, (ll)(i + 1)*(n - i + 1) - 1); } cout << ans << endl; } signed main() { ios::sync_with_stdio(false); cin.tie(0); cout << fixed << setprecision(10); //init(); //int t; cin >> t; rep(i, t)solve(); //while (cin >> n, n)solve(); solve(); stop return 0; }