#ifndef CLASS_FENWICKTREE #define CLASS_FENWICKTREE #include template class fenwick_tree { private: std::size_t n, sz; type* val; public: fenwick_tree() : n(0), sz(0) {}; fenwick_tree(std::size_t n_) : n(n_) { sz = 1; while (sz < n) sz *= 2; val = new type[sz + 1](); } template fenwick_tree(InputIterator first, InputIterator last) : n(last - first) { sz = 1; while (sz < n) sz *= 2; val = new type[sz + 1](); std::size_t cur = 0; for (InputIterator it = first; it != last; ++it) val[++cur] += *it; for (std::size_t i = 1; i < sz; ++i) val[i + (i & ~(i - 1))] += val[i]; } ~fenwick_tree() { delete[] val; } void add(std::size_t pos, type delta) { for (std::size_t i = pos + 1; i <= sz; i += i & ~(i - 1)) { val[i] += delta; } } type getsum(std::size_t r) const { type ans = 0; for (std::size_t i = r; i >= 1; i -= i & ~(i - 1)) { ans += val[i]; } return ans; } type getsum(std::size_t l, std::size_t r) const { return getsum(r) - getsum(l); } std::size_t binary_search(type threshold) const { std::size_t ans = 0; for (std::size_t i = sz / 2; i >= 1; i >>= 1) { if (threshold >= val[ans + i]) { threshold -= val[ans + i]; ans += i; } } return ans; } }; #endif // CLASS_FENWICKTREE #include #include #include using namespace std; int main() { cin.tie(0); ios_base::sync_with_stdio(false); int N; cin >> N; vector A(N); for (int i = 0; i < N; ++i) { cin >> A[i]; } vector SA = A; sort(SA.begin(), SA.end()); SA.erase(unique(SA.begin(), SA.end()), SA.end()); int S = SA.size(); for (int i = 0; i < N; ++i) { A[i] = lower_bound(SA.begin(), SA.end(), A[i]) - SA.begin(); } vector > G(S); for (int i = 0; i < N; ++i) { G[A[i]].push_back(i); } long long ans = 0; for (int i = 0; i < S; ++i) { int M = G[i].size(); vector l(M), r(M); for (int j = 0; j < M; ++j) { l[j] = max(G[i][j] - 2 * M + 2, 0); r[j] = min(G[i][j] + 2 * M, N + 1); } vector cp; cp.insert(cp.begin(), l.begin(), l.end()); cp.insert(cp.begin(), r.begin(), r.end()); sort(cp.begin(), cp.end()); cp.erase(unique(cp.begin(), cp.end()), cp.end()); vector sum(cp.size()); for (int j = 0; j < M; ++j) { l[j] = lower_bound(cp.begin(), cp.end(), l[j]) - cp.begin(); r[j] = lower_bound(cp.begin(), cp.end(), r[j]) - cp.begin(); ++sum[l[j]]; --sum[r[j]]; } for (int j = 1; j < cp.size(); ++j) { sum[j] += sum[j - 1]; } int lp = -1; for (int j = 0; j < cp.size(); ++j) { if (sum[j] >= 1 && lp == -1) { lp = j; } else if (sum[j] == 0 && lp != -1) { vector seq; for (int k = cp[lp]; k < cp[j]; ++k) { seq.push_back(2 * (lower_bound(G[i].begin(), G[i].end(), k) - G[i].begin()) - k); } int mn = *min_element(seq.begin(), seq.end()); for (int k = 0; k < seq.size(); ++k) { seq[k] -= mn; } int mx = *max_element(seq.begin(), seq.end()); fenwick_tree bit(mx + 1); for (int k = 0; k < seq.size(); ++k) { ans += bit.getsum(seq[k]); bit.add(seq[k], 1); } } } } cout << ans << endl; return 0; }