#define _USE_MATH_DEFINES #include using namespace std; #define FOR(i,m,n) for(int i=(m);i<(n);++i) #define REP(i,n) FOR(i,0,n) #define ALL(v) (v).begin(),(v).end() using ll = long long; const int INF = 0x3f3f3f3f; const ll LINF = 0x3f3f3f3f3f3f3f3fLL; const double EPS = 1e-8; const int MOD = 1000000007; // const int MOD = 998244353; const int dy[] = {1, 0, -1, 0}, dx[] = {0, -1, 0, 1}; const int dy8[] = {1, 1, 0, -1, -1, -1, 0, 1}, dx8[] = {0, -1, -1, -1, 0, 1, 1, 1}; template inline bool chmax(T &a, U b) { return a < b ? (a = b, true) : false; } template inline bool chmin(T &a, U b) { return a > b ? (a = b, true) : false; } struct IOSetup { IOSetup() { cin.tie(nullptr); ios_base::sync_with_stdio(false); cout << fixed << setprecision(20); } } iosetup; template struct RMQ { RMQ(int sz, const Monoid UNITY) : UNITY(UNITY) { init(sz); dat.assign((n << 1) - 1, UNITY); } RMQ(const vector &a, const Monoid UNITY) : UNITY(UNITY) { int a_sz = a.size(); init(a_sz); dat.resize((n << 1) - 1); REP(i, a_sz) dat[n - 1 + i] = a[i]; for (int i = n - 2; i >= 0; --i) dat[i] = min(dat[(i << 1) + 1], dat[(i << 1) + 2]); } void update(int node, Monoid val) { node += n - 1; dat[node] = val; while (node > 0) { node = (node - 1) >> 1; dat[node] = min(dat[(node << 1) + 1], dat[(node << 1) + 2]); } } Monoid query(int a, int b) { return query(a, b, 0, 0, n); } int find(int a, int b, Monoid val) { return find(a, b, val, 0, 0, n); } Monoid operator[](const int idx) const { return dat[idx + n - 1]; } private: int n = 1; const Monoid UNITY; vector dat; void init(int sz) { while (n < sz) n <<= 1; } Monoid query(int a, int b, int node, int left, int right) { if (right <= a || b <= left) return UNITY; if (a <= left && right <= b) return dat[node]; return min(query(a, b, (node << 1) + 1, left, (left + right) >> 1), query(a, b, (node << 1) + 2, (left + right) >> 1, right)); } int find(int a, int b, Monoid val, int node, int left, int right) { if (dat[node] > val || right <= a || b <= left) return -1; if (right - left == 1) return node - (n - 1); int res_l = find(a, b, val, (node << 1) + 1, left, (left + right) >> 1); if (res_l != -1) return res_l; return find(a, b, val, (node << 1) + 2, (left + right) >> 1, right); } }; ll solve(const vector &p) { int n = p.size(); ll ans = 0; RMQ rmq(n, INF); rmq.update(p[n - 1], n - 1); vector v{n - 1}; for (int i = n - 2; i >= 0; --i) { while (!v.empty() && p[v.back()] < p[i]) v.pop_back(); // cout << i << ": "; // for (int e : v) cout << e << ' '; // cout << '\n'; int idx = rmq.query(0, p[i] + 1), lb = -1, ub = v.size(); // cout << i << ' ' << idx << '\n'; while (ub - lb > 1) { int mid = (lb + ub) >> 1; (v[mid] < idx ? ub : lb) = mid; } // cout << ub << '\n'; ans += v.size() - ub; // cout << i << ' ' << ans << '\n'; rmq.update(p[i], i); v.emplace_back(i); } return ans; } int main() { int n; cin >> n; vector p(n); REP(i, n) cin >> p[i], --p[i]; ll ans = solve(p); reverse(ALL(p)); ans += solve(p); cout << ans << '\n'; return 0; }