//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,avx512f")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include <iostream>
#include <iomanip>
#include <string>
#include <cmath>
#include <algorithm>
#include <vector>
#include <set>
#include <map>
#include <unordered_map>
#include <unordered_set>
#include <list>
#include <stack>
#include <queue>
#include <bitset>
#include <numeric>
#include <cassert>
#include <memory>
#include <random>
#include <functional>
#include <complex>
#include <immintrin.h>
#include <stdexcept>
#ifdef DEBUG
#include "./CompetitiveProgrammingCpp/Utils/debug.hpp"
#include "./CompetitiveProgrammingCpp/Utils/Timer.hpp"
#include "./CompetitiveProgrammingCpp/Utils/sample.hpp"
#else
#define dump(...)
template<class T>constexpr inline auto d_val(T a, T b) { return a; }
#endif

/* macro */
#define FOR(i, b, e) for(ll i = (ll)(b); i < (ll)(e); ++i)
#define RFOR(i, b, e) for(ll i = (ll)((e)-1); i >= (ll)(b); --i)
#define REP(i, n) FOR(i, 0, (n))
#define RREP(i, n) RFOR(i, 0, (n))
#define REPC(x,c) for(const auto& x:(c))
#define REPI2(it,b,e) for(auto it = (b); it != (e); ++it)
#define REPI(it,c) REPI2(it, (c).begin(), (c).end())
#define RREPI(it,c) REPI2(it, (c).rbegin(), (c).rend())
#define REPI_ERACE2(it, b, e) for(auto it = (b); it != (e);)
#define REPI_ERACE(it, c) REPI_ERACE2(it, (c).begin(), (c).end())
#define ALL(x) (x).begin(),(x).end()
/* macro func */
template<class T>
inline auto sort(T& t) { std::sort(ALL(t)); }
template<class T>
inline auto rsort(T& t) { std::sort((t).rbegin(), (t).rend()); }
template<class T, class S>
inline auto chmax(T& t, const S& s) { if(s > t) { t = s; return true; } return false; }
template<class T, class S>
inline auto chmin(T& t, const S& s) { if(s < t) { t = s; return true; } return false; }
inline auto BR() { std::cout << "\n"; }

/* type define */
using ll = long long;
template<class T>
using V = std::vector<T>;
using VS = V<std::string>;
using VL = V<ll>;
using VVL = V<VL>;
template<class T = ll, class U = T>
using P = std::pair<T, U>;
using PAIR = P<ll>;

/* using std */
using std::cout;
using std::cin;
using std::cerr;
constexpr char endl = '\n';

/* Initial processing  */
struct Preprocessing { Preprocessing() { std::cin.tie(0); std::ios::sync_with_stdio(0); }; }_Preprocessing;

/* define hash */
constexpr unsigned int static_random() { return 1u * __TIME__[0] * __TIME__[1] * __TIME__[3] * __TIME__[4] * __TIME__[6] * __TIME__[7]; }
template<class T> struct Hash { auto operator()(T x) const { return std::hash<T>()(x) ^ static_random(); } };
template<> struct Hash<std::pair<int, int>> { auto operator()(const std::pair<int, int>& x) const { return Hash<long long>()(x.first << 31 | x.second); } };

/* input */
template<class T> std::istream& operator >> (std::istream& is, std::vector<T>& vec) { for(T& x : vec) is >> x; return is; }

/* constant value */
// constexpr ll MOD = 1000000007;
constexpr ll MOD = 998244353;

//=============================================================================================


template<long long X_MAX, class T = long long>
class DynamicLiChaoTree {
    constexpr static T INF = 2e18;

    class Line {
        T a, b;
    public:
        Line(const T& a, const T& b) :a(a), b(b) {}
        Line() :Line(0, INF) {}
        Line(const Line& other) noexcept :Line(other.a, other.b) {}
        Line(Line&& other) noexcept :Line(other) {}
        Line& operator=(Line&& other) noexcept {
            if(this != &other) { a = other.a; b = other.b; }
            return *this;
        }
        auto operator<(const Line& line)const { return a < line.a; }
        auto operator>(const Line& line)const { return line.operator<(*this); }

        auto f(const T& x)const { return a * x + b; }
        auto debug()const {
            if(b == INF) {
                std::cerr << "(" << a << " inf)" << std::endl;
            } else {
                std::cerr << "(" << a << " " << b << ")" << std::endl;
            }
        }
    };

    struct Node {
        Line line;
        std::unique_ptr<Node> left;
        std::unique_ptr<Node> right;

        Node(const Line& line) :line(line) {}
        auto f(const T& x)const { return line.f(x); }
    };

    std::unique_ptr<Node> m_root;

    auto addLine(std::unique_ptr<Node>& node, Line&& line, long long l, long long r) {
        if(!node) { node = std::make_unique<Node>(line); return; }

        auto m = (l + 1 == r) ? l : (l + r) / 2;
        if(line.f(m) < node->f(m)) { std::swap(node->line, line); }
        if(l + 1 == r) { return; }
        if(line > node->line) {
            addLine(node->left, std::move(line), l, m);
        } else if(line < node->line) {
            addLine(node->right, std::move(line), m, r);
        }
    }
    auto addSegment(std::unique_ptr<Node>& node, const Line& line, T l, T r, T sl, T sr) {
        if(sr <= l || r <= sl) { return; }
        if(l <= sl && sr <= r) { addLine(node, Line(line), sl, sr); return; }
        auto m = (sl + sr) / 2;
        if(!node) { node = std::make_unique<Node>(Line()); }
        addSegment(node->left, line, l, r, sl, m);
        addSegment(node->right, line, l, r, m, sr);
    }

    auto query(const std::unique_ptr<Node>& node, const T& x, long long l, long long r) const {
        if(!node) { return Line().f(x); }
        auto m = (l + r) / 2;
        return std::min(
            node->f(x),
            (x < m) ? query(node->left, x, l, m) : query(node->right, x, m, r)
        );
    }
public:
    DynamicLiChaoTree() {}

    auto addLine(const T& a, const T& b) { addLine(m_root, Line(a, b), -X_MAX, X_MAX + 1); }
    auto addLine(const std::pair<T, T>& line) { addLine(line.first, line.second); }
    [[deprecated("This method is too slow. Please use LiChaoTree and not DynamicLiChaoTree.")]]
    auto addSegment(const T& a, const T& b, const T& l, const T& r) { addSegment(m_root, Line(a, b), l, r + 1, -X_MAX, X_MAX + 1); }
    auto addSegment(const std::pair<T, T>& line, const T& l, const T& r) { addSegment(line.first, line.second, l, r); }
    auto query(const T& x) const { return query(m_root, x, -X_MAX, X_MAX + 1); }

    auto debug(const std::unique_ptr<Node>& node, int size)const {
        if(size == 0) { std::cerr << "-- li chao tree --" << std::endl; }
        if(!node) { return; }
        for(int i = 0; i < size; ++i) { std::cerr << "- "; }
        node->line.debug();
        if(node->left) { std::cout << "L"; debug(node->left, size + 1); }
        if(node->right) { std::cout << "R"; debug(node->right, size + 1); }
    }
    auto debug()const { debug(m_root, 0); }
};


signed main() {
    ll n;
    cin >> n;
    VL a(n);
    cin >> a;

    auto lct = DynamicLiChaoTree<static_cast<ll>(1e6)>();
    VL dp(n, 1e18);
    lct.addLine(-a[0], 0);
    FOR(i, 1, n) {
        dp[i] = lct.query(a[i]);
        chmin(dp[i], 0);
        lct.addLine(-a[i], dp[i]);
    }
    cout << -(*std::min_element(ALL(dp))) << endl;
}