// need #include #include // data structure #include #include #include #include #include #include #include #include #include //#include #include #include #include // stream //#include //#include //#include #include // etc #include #include #include #include //#include #include #include // input #define INIT std::ios::sync_with_stdio(false);std::cin.tie(0); #define VAR(type, ...)type __VA_ARGS__;MACRO_VAR_Scan(__VA_ARGS__); template void MACRO_VAR_Scan(T& t) { std::cin >> t; } templatevoid MACRO_VAR_Scan(First& first, Rest&...rest) { std::cin >> first; MACRO_VAR_Scan(rest...); } #define VEC_ROW(type, n, ...)std::vector __VA_ARGS__;MACRO_VEC_ROW_Init(n, __VA_ARGS__); for(int w=0; w void MACRO_VEC_ROW_Init(int n, T& t) { t.resize(n); } templatevoid MACRO_VEC_ROW_Init(int n, First& first, Rest&...rest) { first.resize(n); MACRO_VEC_ROW_Init(n, rest...); } template void MACRO_VEC_ROW_Scan(int p, T& t) { std::cin >> t[p]; } templatevoid MACRO_VEC_ROW_Scan(int p, First& first, Rest&...rest) { std::cin >> first[p]; MACRO_VEC_ROW_Scan(p, rest...); } #define VEC(type, c, n) std::vector c(n);for(auto& i:c)std::cin>>i; #define MAT(type, c, m, n) std::vector> c(m, std::vector(n));for(auto& R:c)for(auto& w:R)std::cin>>w; // output #define OUT(dist) std::cout<<(dist); #define FOUT(n, dist) std::cout<=(a);--w) #define REP(w, n) for(int w=0;w=0;--w) #define FORLL(w, a, n) for(ll w=ll(a);w=ll(a);--w) #define REPLL(w, n) for(ll w=0;w=0;--w) #define IN(a, x, b) (a<=x && x inline T CHMAX(T& a, const T b) { return a = (a < b) ? b : a; } template inline T CHMIN(T& a, const T b) { return a = (a > b) ? b : a; } #define EXCEPTION(msg) throw std::string("Exception : " msg " [ in ") + __func__ + " : " + std::to_string(__LINE__) + " lines ]" #define TRY(cond, msg) try {if (cond) EXCEPTION(msg);}catch (std::string s) {std::cerr << s << std::endl;} //void CHECKTIME(std::function f) { auto start = std::chrono::system_clock::now(); f(); auto end = std::chrono::system_clock::now(); auto res = std::chrono::duration_cast((end - start)).count(); std::cerr << "[Time:" << res << "ns (" << res / (1.0e9) << "s)]\n"; } // test template std::vector> VV(int n, int m, T init = T()) { return std::vector>(n, std::vector(m, init)); } template std::ostream& operator<<(std::ostream& os, std::pair p) { os << "(" << p.first << ", " << p.second << ")"; return os; } // type/const #define int ll using ll = long long; using ull = unsigned long long; using ld = long double; using PAIR = std::pair; using PAIRLL = std::pair; constexpr int INFINT = 1 << 30; // 1.07x10^ 9 constexpr int INFINT_LIM = (1LL << 31) - 1; // 2.15x10^ 9 constexpr ll INFLL = 1LL << 60; // 1.15x10^18 constexpr ll INFLL_LIM = (1LL << 62) - 1 + (1LL << 62); // 9.22x10^18 constexpr double EPS = 1e-10; constexpr int MOD = 1000000007; constexpr double PI = 3.141592653589793238462643383279; template void FILL(T(&a)[N], const T& val) { for (auto& x : a) x = val; } template void FILL(ARY(&a)[N][M], const T& val) { for (auto& b : a) FILL(b, val); } template void FILL(std::vector& a, const T& val) { for (auto& x : a) x = val; } template void FILL(std::vector>& a, const T& val) { for (auto& b : a) FILL(b, val); } // ------------>8------------------------------------->8------------ // ------------>8------------ SegmentTree ------------>8------------ // -- Query Type enum. enum QUERY { SUM, MAX, MIN }; template class SegmentTree { private: int ARY_SIZE; T init_val; std::vector ary; std::function func; public: SegmentTree(int n, QUERY qtype) : ARY_SIZE(1) { init(n, qtype); } SegmentTree(int n, T init_val, QUERY qtype) : ARY_SIZE(1) { init(n, init_val, qtype); } void init(int n, QUERY qtype) { T init_val; switch (qtype) { case SUM: init_val = 0; break; case MAX: init_val = std::numeric_limits::lowest(); break; case MIN: init_val = std::numeric_limits::max(); break; default: struct INVALID_QUERY_TYPE_ERROR {}; throw INVALID_QUERY_TYPE_ERROR(); break; } init(n, init_val, qtype); } void init(int n, T init_val, QUERY qtype) { std::function f; switch (qtype) { case SUM: f = [](T l, T r) {return l + r; }; break; case MAX: f = [](T l, T r) {return std::max(l, r); }; break; case MIN: f = [](T l, T r) {return std::min(l, r); }; break; default: struct INVALID_QUERY_TYPE_ERROR {}; throw INVALID_QUERY_TYPE_ERROR(); break; } init(n, init_val, f); } void init(int n, T init_val, std::function f) { while (ARY_SIZE < n) ARY_SIZE <<= 1; ARY_SIZE = ARY_SIZE * 2 - 1; ary.resize(ARY_SIZE, init_val); this->init_val = init_val; func = f; } // -- a[i] = val; void update(int i, T val) { i += ARY_SIZE / 2; ary[i] = val; while (i > 0) { i = (i - 1) / 2; ary[i] = func(ary[2 * i + 1], ary[2 * i + 2]); } } // -- a[i] += val; void add(int i, T val) { i += ARY_SIZE / 2; ary[i] += val; while (i > 0) { i = (i - 1) / 2; ary[i] = func(ary[2 * i + 1], ary[2 * i + 2]); } } // -- 区間[a, b)のfuncの返す値を返す (query_(a, b, 0, 0, n)と呼び出す) T query_(int a, int b, int i, int l, int r) { if (r <= a || b <= l) return init_val; if (a <= l && r <= b) return ary[i]; else { T vl = query_(a, b, 2 * i + 1, l, (l + r) / 2); T vr = query_(a, b, 2 * i + 2, (l + r) / 2, r); return func(vl, vr); } } // -- [a, b) T query(int a, int b) { return query_(a, b, 0, 0, ARY_SIZE / 2 + 1); } T operator[](int i) { return ary[i + ARY_SIZE / 2]; } void debug_show() { for (int i = ARY_SIZE / 2; i < ARY_SIZE; ++i) std::cerr << ary[i] << " "; std::cerr << "\n"; } }; using ST = SegmentTree; // ------------8<------------ SegmentTree ------------8<------------ signed main() { INIT; VAR(int, n); VEC(int, m, n); ST st(n, SUM); int ans = 0; REP(i, n) { --m[i]; ans += st.query(m[i], n); st.update(m[i], st.query(m[i], m[i] + 1) + 1); } OUT(ans)BR; return 0; }