#ifdef ONLINE_JUDGE
#include <bits/stdc++.h>

#include <atcoder/all>
#else
#include <mylibs/all.h>
#endif

inline std::ostream& operator<<(std::ostream& os, __int128_t val) noexcept {
    std::string s;
    bool neg = val < 0;
    if (val < 0) {
        val *= -1;
    }
    if (val == 0) {
        s += '0';
    } else {
        while (val > 0) {
            s += '0' + val % 10;
            val /= 10;
        }
    }
    reverse(s.begin(), s.end());
    if (neg) s = "-" + s;
    return os << s;
}
inline std::istream& operator>>(std::istream& is, __int128_t& val) noexcept {
    std::string s;
    is >> s;
    bool neg = false;
    if (s[0] == '-') {
        neg = true;
        s = s.substr(1);
    }
    val = 0;
    for (auto c : s) {
        val *= 10;
        val += c - '0';
    }
    if (neg) val *= -1;
    return is;
}
__int128_t stolll(std::string s) {
    __int128_t res = 0;
    bool neg = false;
    if (s[0] == '-') {
        neg = true;
        s = s.substr(1);
    }
    for (auto c : s) {
        res *= 10;
        res += c - '0';
    }
    if (neg) res *= -1;
    return res;
}
std::string to_string(__int128_t x) {
    std::string s;
    bool neg = x < 0;
    if (x < 0) {
        x *= -1;
    }
    if (x == 0) {
        s += '0';
    } else {
        while (x > 0) {
            s += '0' + x % 10;
            x /= 10;
        }
    }
    reverse(s.begin(), s.end());
    if (neg) s = "-" + s;
    return s;
}

using ll = long long;
using lll = __int128_t;
#define rep(i, n) for (int i = 0, i##_len = (n); i < i##_len; ++i)
#define reps(i, n) for (int i = 1, i##_len = (n); i <= i##_len; ++i)
#define rrep(i, n) for (int i = ((int)(n)-1); i >= 0; --i)
#define rreps(i, n) for (int i = ((int)(n)); i > 0; --i)
#define rep2(i, s, n) for (int i = (s); i < (int)(n); i++)
#define repc2(i, s, n) for (int i = (s); i <= (int)(n); i++)
#define length(v) ((int)(v).size())
constexpr int inf = 2'000'000'000;
constexpr ll linf = 4'000'000'000'000'000'000, M7 = 1'000'000'007, M9 = 998'244'353;
#define all(v) begin(v), end(v)
#define rall(v) rbegin(v), rend(v)
using namespace std;
using namespace atcoder;

// clang-format off
using vint = vector<int>;using vvint = vector<vector<int>>;using vvvint = vector<vector<vector<int>>>;
using vll = vector<ll>;using vvll = vector<vector<ll>>;using vvvll = vector<vector<vector<ll>>>;
using vlll = vector<lll>;using vvlll = vector<vector<lll>>;using vvvlll = vector<vector<vector<lll>>>;
using vchar = vector<char>;using vvchar = vector<vector<char>>;using vvvchar = vector<vector<vector<char>>>;
using vstr = vector<string>;using vvstr = vector<vector<string>>;using vvvstr = vector<vector<vector<string>>>;
using vpi = vector<pair<int, int>>;using vvpi = vector<vector<pair<int, int>>>;using vvpint = vector<vector<pair<int, int>>>;
using vpl = vector<pair<ll, ll>>;using vvpl = vector<vector<pair<ll, ll>>>;using vvplint = vector<vector<pair<ll, int>>>;
using vbool = vector<bool>;using vvbool = vector<vector<bool>>;using vvvbool = vector<vector<vector<bool>>>;

#define Vec(type, ...) __make_vec<type>(__VA_ARGS__)
template <class T> vector<T> __make_vec(size_t a) {return vector<T>(a);}template <class T, class... Ts>
auto __make_vec(size_t a, Ts... ts) {return vector<decltype(__make_vec<T>(ts...))>(a, __make_vec<T>(ts...));}
#define VecI(init, type, ...) __make_vecI<type, init>(__VA_ARGS__)
template <class T, T init>vector<T> __make_vecI(size_t a) {return vector<T>(a, init);}
template <class T, T init, class... Ts>
auto __make_vecI(size_t a, Ts... ts) {return vector<decltype(__make_vecI<T, init>(ts...))>(a, __make_vecI<T, init>(ts...));}

template <typename T, typename U>inline ostream& operator<<(ostream& os, const pair<T, U>& p) noexcept {return os << p.first << " " << p.second;}
inline ostream& operator<<(ostream& os, const modint& m) noexcept { return os << m.val(); }
template <int M>inline ostream& operator<<(ostream& os, const static_modint<M>& m) noexcept { return os << m.val(); }

template <typename T> struct is_static_modint : std::false_type {}; template <int MOD> struct is_static_modint<static_modint<MOD>> : std::true_type {};
template <template <typename...> typename C, typename Number>concept MyContainer = std::is_same_v<C<Number>, std::vector<Number>> || std::is_same_v<C<Number>, std::deque<Number>> || std::is_same_v<C<Number>, std::set<Number>> || std::is_same_v<C<Number>, std::unordered_set<Number>> || std::is_same_v<C<Number>, std::unordered_multiset<Number>> || std::is_same_v<C<Number>, std::multiset<Number>>;
template <typename Number>concept MyNumber = std::is_same_v<Number, int> || std::is_same_v<Number, ll> || std::is_same_v<Number, char> || std::is_same_v<Number, modint> || is_static_modint<Number>::value;
template <template <typename...> typename C, typename Number>concept MyContainerNumber = MyContainer<C, Number> && MyNumber<Number>;
template <template <typename...> typename OutCon, template <typename...> typename InCon, typename Number>concept MyNestedContainerNumber = MyContainer<OutCon, InCon<Number>> && MyContainerNumber<InCon, Number>;
template <template <typename...> typename C, typename Number>requires MyContainerNumber<C, Number>std::ostream& operator<<(std::ostream& os, const C<Number>& t) {auto itr = t.begin();auto end = t.end();if (itr != end) {os << *itr++;for (; itr != end; ++itr) os << ' ' << *itr;}return os;}
template <template <typename...> typename OutCon, template <typename...> typename InCon, typename Number>requires MyNestedContainerNumber<OutCon, InCon, Number>std::ostream& operator<<(std::ostream& os, const OutCon<InCon<Number>>& t) {auto itr = t.begin();auto end = t.end();if (itr != end) {os << *itr++;for (; itr != end; ++itr) os << '\n' << *itr;}return os;}
template <typename T, typename U>istream& operator>>(istream& is, pair<T, U>& p) {return is >> p.first >> p.second;}
template <typename T>istream& operator>>(istream& is, vector<T>& v) {for (auto& e : v) is >> e;return is;}
void inp() {}
template <typename T, typename... Args>void inp(T& a, Args&... args) {cin >> a, inp(args...);}
template <typename T>void inp1(vector<T>& v, int offset = 1, int len = -1) {if (len == -1) len = int(v.size()) - offset;assert(offset >= 0 && len >= 0);for (int i = offset; i < offset + len; ++i) cin >> v[i];}
template <typename T>void oup(const T& a) {cout << a << "\n";}
template <typename T, typename... Args>void oup(const T& a, const Args&... args) {cout << a << " ", oup(args...);}

inline string YesNo(bool cond) { return cond ? "Yes" : "No"; }
inline auto add1(auto vec, ll offset = 1) {for (auto& e : vec) e += offset;return vec;}
#ifdef ONLINE_JUDGE
#define debug(...)
#else
#define debug(...) cerr << "<" << #__VA_ARGS__ << ">: ", debug_out(__VA_ARGS__)
template <typename T>void debug_out(T t) {cerr << t << "\n";}
template <typename T, typename... Args>void debug_out(T t, Args... args) {cerr << t << ", ";debug_out(args...);}
#endif

#ifdef ONLINE_JUDGE
#define todo(...) static_assert(false)
#else
#define todo(...)
#endif
// clang-format on

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    lll n;
    cin >> n;
    oup(n * (n + 1) / 2);
}