#define MOD_TYPE 2

#include <bits/stdc++.h>
using namespace std;
#include <atcoder/all>
// #include <atcoder/lazysegtree>
// #include <atcoder/modint>
// #include <atcoder/segtree>
using namespace atcoder;
#if 0
#include <boost/multiprecision/cpp_dec_float.hpp>
#include <boost/multiprecision/cpp_int.hpp>
using Int = boost::multiprecision::cpp_int;
using lld = boost::multiprecision::cpp_dec_float_100;
#endif
#if 0
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tag_and_trait.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/rope>
using namespace __gnu_pbds;
using namespace __gnu_cxx;
template <typename T>
using extset =
    tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
#endif
#if 1
#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#endif
#pragma region Macros
using ll = long long int;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pld = pair<ld, ld>;
template <typename Q_type>
using smaller_queue = priority_queue<Q_type, vector<Q_type>, greater<Q_type>>;
#if MOD_TYPE == 1
constexpr ll MOD = ll(1e9 + 7);
#else
#if MOD_TYPE == 2
constexpr ll MOD = 998244353;
#else
constexpr ll MOD = 1000003;
#endif
#endif
using mint = static_modint<MOD>;
constexpr int INF = (int)1e9 + 10;
constexpr ll LINF = (ll)4e18;
const double PI = acos(-1.0);
constexpr ld EPS = 1e-10;
constexpr int Dx[] = {0, 0, -1, 1, -1, 1, -1, 1, 0};
constexpr int Dy[] = {1, -1, 0, 0, -1, -1, 1, 1, 0};
#define REP(i, m, n) for (ll i = m; i < (ll)(n); ++i)
#define rep(i, n) REP(i, 0, n)
#define REPI(i, m, n) for (int i = m; i < (int)(n); ++i)
#define repi(i, n) REPI(i, 0, n)
#define RREP(i, m, n) for (ll i = n - 1; i >= m; i--)
#define rrep(i, n) RREP(i, 0, n)
#define YES(n) cout << ((n) ? "YES" : "NO") << "\n"
#define Yes(n) cout << ((n) ? "Yes" : "No") << "\n"
#define all(v) v.begin(), v.end()
#define NP(v) next_permutation(all(v))
#define dbg(x) cerr << #x << ":" << x << "\n";
#define UNIQUE(v) v.erase(unique(all(v)), v.end())
struct io_init {
  io_init() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << setprecision(20) << setiosflags(ios::fixed);
  };
} io_init;
template <typename T>
inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <typename T>
inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
inline ll floor(ll a, ll b) {
  if (b < 0) a *= -1, b *= -1;
  if (a >= 0) return a / b;
  return -((-a + b - 1) / b);
}
inline ll ceil(ll a, ll b) { return floor(a + b - 1, b); }
template <typename A, size_t N, typename T>
inline void Fill(A (&array)[N], const T &val) {
  fill((T *)array, (T *)(array + N), val);
}
template <typename T>
vector<T> compress(vector<T> &v) {
  vector<T> val = v;
  sort(all(val)), val.erase(unique(all(val)), val.end());
  for (auto &&vi : v) vi = lower_bound(all(val), vi) - val.begin();
  return val;
}
template <typename T, typename U>
constexpr istream &operator>>(istream &is, pair<T, U> &p) noexcept {
  is >> p.first >> p.second;
  return is;
}
template <typename T, typename U>
constexpr ostream &operator<<(ostream &os, pair<T, U> p) noexcept {
  os << p.first << " " << p.second;
  return os;
}
ostream &operator<<(ostream &os, mint m) {
  os << m.val();
  return os;
}
ostream &operator<<(ostream &os, modint m) {
  os << m.val();
  return os;
}
template <typename T>
constexpr istream &operator>>(istream &is, vector<T> &v) noexcept {
  for (int i = 0; i < v.size(); i++) is >> v[i];
  return is;
}
template <typename T>
constexpr ostream &operator<<(ostream &os, vector<T> &v) noexcept {
  for (int i = 0; i < v.size(); i++)
    os << v[i] << (i + 1 == v.size() ? "" : " ");
  return os;
}
template <typename T>
constexpr void operator--(vector<T> &v, int) noexcept {
  for (int i = 0; i < v.size(); i++) v[i]--;
}
random_device seed_gen;
mt19937_64 engine(seed_gen());
inline ll randInt(ll l, ll r) { return engine() % (r - l + 1) + l; }
struct BiCoef {
  vector<mint> fact_, inv_, finv_;
  BiCoef(int n) noexcept : fact_(n, 1), inv_(n, 1), finv_(n, 1) {
    fact_.assign(n, 1), inv_.assign(n, 1), finv_.assign(n, 1);
    for (int i = 2; i < n; i++) {
      fact_[i] = fact_[i - 1] * i;
      inv_[i] = -inv_[MOD % i] * (MOD / i);
      finv_[i] = finv_[i - 1] * inv_[i];
    }
  }
  mint C(ll n, ll k) const noexcept {
    if (n < k || n < 0 || k < 0) return 0;
    return fact_[n] * finv_[k] * finv_[n - k];
  }
  mint P(ll n, ll k) const noexcept { return C(n, k) * fact_[k]; }
  mint H(ll n, ll k) const noexcept { return C(n + k - 1, k); }
  mint Ch1(ll n, ll k) const noexcept {
    if (n < 0 || k < 0) return 0;
    mint res = 0;
    for (int i = 0; i < n; i++)
      res += C(n, i) * mint(n - i).pow(k) * (i & 1 ? -1 : 1);
    return res;
  }
  mint fact(ll n) const noexcept {
    if (n < 0) return 0;
    return fact_[n];
  }
  mint inv(ll n) const noexcept {
    if (n < 0) return 0;
    return inv_[n];
  }
  mint finv(ll n) const noexcept {
    if (n < 0) return 0;
    return finv_[n];
  }
};
BiCoef bc(1000010);
#pragma endregion

// -------------------------------

template <typename T, bool isMin>
class LiChaoTree {
  int n;
  vector<T> xs, p, q;
  vector<bool> u;
  int INFi;
  T INFT;

  void _add_line(T a, T b, int k, int l, int r) {
    while (r - l > 0) {
      int m = (l + r) >> 1;
      if (!u[k]) {
        p[k] = a;
        q[k] = b;
        u[k] = true;
        return;
      }

      T lx = xs[l], mx = xs[m], rx = xs[r - 1];
      T pk = p[k], qk = q[k];
      bool left = (a * lx + b < pk * lx + qk);
      bool mid = (a * mx + b < pk * mx + qk);
      bool right = (a * rx + b < pk * rx + qk);
      if (left && right) {
        p[k] = a;
        q[k] = b;
        return;
      }
      if (!left && !right) {
        return;
      }
      if (mid) {
        swap(p[k], a);
        swap(q[k], b);
      }
      if (left != mid) {
        k = 2 * k + 1;
        r = m;
      } else {
        k = 2 * k + 2;
        l = m;
      }
    }
  }

  T _query(int k, T x) {
    k += n - 1;
    T s = u[k] ? p[k] * x + q[k] : INFT;
    while (k > 0) {
      k = (k - 1) / 2;
      if (u[k]) {
        T r = p[k] * x + q[k];
        s = min(s, r);
      }
    }
    return s;
  }

 public:
  LiChaoTree(vector<T> &ps, T INFT = 4e18, int INFi = 1e9 + 10)
      : INFT(INFT), INFi(INFi) {
    n = 1;
    while (n < ps.size()) n <<= 1;
    xs.resize(2 * n - 1);
    p.resize(2 * n - 1);
    q.resize(2 * n - 1);
    u.assign(2 * n - 1, false);
    for (int i = 0; i < ps.size(); ++i) xs[i] = ps[i];
    for (int i = ps.size(); i < 2 * n - 1; ++i) xs[i] = INFi;
  }

  void add_line(T a, T b) {
    if (!isMin) a *= -1, b *= -1;
    _add_line(a, b, 0, 0, n);
  }

  void add_segment_line(T a, T b, int l, int r) {
    if (!isMin) a *= -1, b *= -1;
    T l0 = l + n, r0 = r + n;
    T s0 = l, t0 = r, sz = 1;
    while (l0 < r0) {
      if (r0 & 1) {
        --r0;
        t0 -= sz;
        _add_line(a, b, r0 - 1, t0, t0 + sz);
      }
      if (l0 & 1) {
        _add_line(a, b, l0 - 1, s0, s0 + sz);
        ++l0;
        s0 += sz;
      }
      l0 >>= 1;
      r0 >>= 1;
      sz <<= 1;
    }
  }

  inline T query(int i) {
    if (!isMin) return -_query(i, xs[i]);
    return _query(i, xs[i]);
  }
};

void solve() {
  int n;
  cin >> n;
  vector<ll> q(n);
  cin >> q;
  vector<ll> dp(200001, 0);
  vector<ll> ps;
  REP(i, -100000, 100001) ps.push_back(i);
  LiChaoTree<ll, false> lct(ps);
  int ofs = 100000;
  rep(i, n) {
    int qi = q[i];
    if (i == 0) {
      lct.add_line(qi, dp[qi + ofs]);
      continue;
    }
    dp[qi + ofs] = lct.query(qi + ofs);
    lct.add_line(qi, dp[qi + ofs]);
  }
  cout << *max_element(all(dp)) << "\n";
}

int main() { solve(); }