#include #ifdef LOCAL #include #else #define debug(...) void(0) #endif struct Line { mutable long long k, m, p; bool operator<(const Line& o) const { return k < o.k; } bool operator<(long long x) const { return p < x; } }; template struct LineContainer : std::multiset> { // (for doubles, use inf = 1/.0, div(a,b) = a/b) const long long inf = LLONG_MAX / 2; long long div(long long a, long long b) { // floored division return a / b - ((a ^ b) < 0 && a % b); } bool isect(iterator x, iterator y) { if (y == end()) { x->p = inf; return false; } if (x->k == y->k) x->p = x->m > y->m ? inf : -inf; else x->p = div(y->m - x->m, x->k - y->k); return x->p >= y->p; } void add(long long k, long long m) { if (isMin) k = -k, m = -m; auto z = insert({k, m, 0}), y = z++, x = y; while (isect(y, z)) z = erase(z); if (x != begin() && isect(--x, y)) isect(x, y = erase(y)); while ((y = x) != begin() && (--x)->p >= y->p) isect(x, erase(y)); } long long query(long long x) { assert(!empty()); auto l = *lower_bound(x); long long s = 1; if (isMin) s = -1; return s * (l.k * x + l.m); } }; using namespace std; typedef long long ll; #define all(x) begin(x), end(x) constexpr int INF = (1 << 30) - 1; constexpr long long IINF = (1LL << 60) - 1; constexpr int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1}; template istream& operator>>(istream& is, vector& v) { for (auto& x : v) is >> x; return is; } template ostream& operator<<(ostream& os, const vector& v) { auto sep = ""; for (const auto& x : v) os << exchange(sep, " ") << x; return os; } template bool chmin(T& x, U&& y) { return y < x and (x = forward(y), true); } template bool chmax(T& x, U&& y) { return x < y and (x = forward(y), true); } template void mkuni(vector& v) { sort(begin(v), end(v)); v.erase(unique(begin(v), end(v)), end(v)); } template int lwb(const vector& v, const T& x) { return lower_bound(begin(v), end(v), x) - begin(v); } int main() { ios::sync_with_stdio(false); cin.tie(nullptr); int N; cin >> N; LineContainer LC; ll ans = 0; LC.add(0, 0); for (int i = 0; i < N; i++) { int Q; cin >> Q; ll val = LC.query(Q); chmax(ans, val); LC.add(Q, val); } cout << ans << '\n'; return 0; }