#include <bits/stdc++.h> using namespace std; #define rep(i, n) for (int i = 0; i < (n); i++) #define per(i, n) for (int i = (n)-1; i >= 0; i--) #define rep2(i, l, r) for (int i = (l); i < (r); i++) #define per2(i, l, r) for (int i = (r)-1; i >= (l); i--) #define each(e, v) for (auto &e : v) #define MM << " " << #define pb push_back #define eb emplace_back #define all(x) begin(x), end(x) #define rall(x) rbegin(x), rend(x) #define sz(x) (int)x.size() using ll = long long; using pii = pair<int, int>; using pil = pair<int, ll>; using pli = pair<ll, int>; using pll = pair<ll, ll>; template <typename T> using minheap = priority_queue<T, vector<T>, greater<T>>; template <typename T> using maxheap = priority_queue<T>; template <typename T> bool chmax(T &x, const T &y) { return (x < y) ? (x = y, true) : false; } template <typename T> bool chmin(T &x, const T &y) { return (x > y) ? (x = y, true) : false; } template <typename T> int flg(T x, int i) { return (x >> i) & 1; } int pct(int x) { return __builtin_popcount(x); } int pct(ll x) { return __builtin_popcountll(x); } int topbit(int x) { return (x == 0 ? -1 : 31 - __builtin_clz(x)); } int topbit(ll x) { return (x == 0 ? -1 : 63 - __builtin_clzll(x)); } int botbit(int x) { return (x == 0 ? -1 : __builtin_ctz(x)); } int botbit(ll x) { return (x == 0 ? -1 : __builtin_ctzll(x)); } template <typename T> void print(const vector<T> &v, T x = 0) { int n = v.size(); for (int i = 0; i < n; i++) cout << v[i] + x << (i == n - 1 ? '\n' : ' '); if (v.empty()) cout << '\n'; } template <typename T> void printn(const vector<T> &v, T x = 0) { int n = v.size(); for (int i = 0; i < n; i++) cout << v[i] + x << '\n'; } template <typename T> int lb(const vector<T> &v, T x) { return lower_bound(begin(v), end(v), x) - begin(v); } template <typename T> int ub(const vector<T> &v, T x) { return upper_bound(begin(v), end(v), x) - begin(v); } template <typename T> void rearrange(vector<T> &v) { sort(begin(v), end(v)); v.erase(unique(begin(v), end(v)), end(v)); } template <typename T> vector<int> id_sort(const vector<T> &v, bool greater = false) { int n = v.size(); vector<int> ret(n); iota(begin(ret), end(ret), 0); sort(begin(ret), end(ret), [&](int i, int j) { return greater ? v[i] > v[j] : v[i] < v[j]; }); return ret; } template <typename T> void reorder(vector<T> &a, const vector<int> &ord) { int n = a.size(); vector<T> b(n); for (int i = 0; i < n; i++) b[i] = a[ord[i]]; swap(a, b); } template <typename T> T floor(T x, T y) { assert(y != 0); if (y < 0) x = -x, y = -y; return (x >= 0 ? x / y : (x - y + 1) / y); } template <typename T> T ceil(T x, T y) { assert(y != 0); if (y < 0) x = -x, y = -y; return (x >= 0 ? (x + y - 1) / y : x / y); } template <typename S, typename T> pair<S, T> operator+(const pair<S, T> &p, const pair<S, T> &q) { return make_pair(p.first + q.first, p.second + q.second); } template <typename S, typename T> pair<S, T> operator-(const pair<S, T> &p, const pair<S, T> &q) { return make_pair(p.first - q.first, p.second - q.second); } template <typename S, typename T> istream &operator>>(istream &is, pair<S, T> &p) { S a; T b; is >> a >> b; p = make_pair(a, b); return is; } template <typename S, typename T> ostream &operator<<(ostream &os, const pair<S, T> &p) { return os << p.first << ' ' << p.second; } struct io_setup { io_setup() { ios_base::sync_with_stdio(false); cin.tie(NULL); cout << fixed << setprecision(15); cerr << fixed << setprecision(15); } } io_setup; constexpr int inf = (1 << 30) - 1; constexpr ll INF = (1LL << 60) - 1; // constexpr int MOD = 1000000007; constexpr int MOD = 998244353; template <typename T, T min_x, T max_x, bool is_min = true> struct Li_Chao_Tree { struct Line { T a, b; Line(const T &a, const T &b) : a(a), b(b) {} T get(const T &x) const { return a * x + b; } }; struct Node { Node *lch, *rch; Line l; Node(const Line &l) : lch(NULL), rch(NULL), l(l) {} Node(const T &a, const T &b) : lch(NULL), rch(NULL), l(a, b) {} }; Node *root; const T INF_T = numeric_limits<T>::max() / 2; Li_Chao_Tree() : root(NULL) {} ~Li_Chao_Tree() { rec_delete(root); } void rec_delete(Node *now) { if (!now) return; rec_delete(now->lch), rec_delete(now->rch); delete now; } Node *add_line(const Line &k, Node *now, const T &l, const T &r) { if (!now) return new Node(k); T l1 = now->l.get(l), l2 = k.get(l); T r1 = now->l.get(r), r2 = k.get(r); if (l1 <= l2 && r1 <= r2) return now; if (l1 >= l2 && r1 >= r2) { now->l = k; return now; } T m = (l + r - 1) / 2; T m1 = now->l.get(m), m2 = k.get(m); if (m1 > m2) { if (l1 <= l2) { now->lch = add_line(now->l, now->lch, l, m); } else { now->rch = add_line(now->l, now->rch, m + 1, r); } now->l = k; } else { if (l1 >= l2) { now->lch = add_line(k, now->lch, l, m); } else { now->rch = add_line(k, now->rch, m + 1, r); } } return now; } // 直線 y = ax+b を追加 void add_line(const T &a, const T &b) { Line k(is_min ? a : -a, is_min ? b : -b); root = add_line(k, root, min_x, max_x); } Node *add_segment(const T &s, const T &t, const Line &k, Node *now, const T &l, const T &r) { if (r < s || t < l) return now; if (s <= l && r <= t) return add_line(k, now, l, r); T m = (l + r - 1) / 2; if (!now) now = new Node(0, INF_T); now->lch = add_segment(s, t, k, now->lch, l, m); now->rch = add_segment(s, t, k, now->rch, m + 1, r); return now; } // [l,r) に直線 y = ax+b を追加 void add_segment(const T &l, const T &r, const T &a, const T &b) { Line k(is_min ? a : -a, is_min ? b : -b); root = add_segment(l, r - 1, k, root, min_x, max_x); } T query(const T &x, Node *now, const T &l, const T &r) const { if (!now) return INF_T; if (l == r) return now->l.get(x); T m = (l + r - 1) / 2; if (x <= m) return min(now->l.get(x), query(x, now->lch, l, m)); return min(now->l.get(x), query(x, now->rch, m + 1, r)); } T query(const T &x) const { T ret = query(x, root, min_x, max_x); return is_min ? ret : -ret; } }; void solve() { int N; cin >> N; vector<ll> Q(N); rep(i, N) cin >> Q[i]; const ll MAX = 300000; Li_Chao_Tree<ll, -MAX, MAX, false> lct; lct.add_line(0, 0); ll ans = 0; rep(i, N) { ll tmp = lct.query(Q[i]); chmax(ans, tmp); lct.add_line(Q[i], tmp); } cout << ans << '\n'; } int main() { int T = 1; // cin >> T; while (T--) solve(); }