//#define NDEBUG
#include <cstddef>
#include <cstdint>
#include <iostream>
#include <vector>

namespace n91 {

  using i8 = std::int_fast8_t;
  using i32 = std::int_fast32_t;
  using i64 = std::int_fast64_t;
  using u8 = std::uint_fast8_t;
  using u32 = std::uint_fast32_t;
  using u64 = std::uint_fast64_t;
  using isize = std::ptrdiff_t;
  using usize = std::size_t;

  constexpr usize operator"" _z(unsigned long long x) noexcept {
    return static_cast<usize>(x);
  }

  class rep {
    const usize f, l;

  public:
    class itr {
      friend rep;
      usize i;
      constexpr itr(const usize x) noexcept : i(x) {}

    public:
      void operator++() noexcept { ++i; }
      constexpr usize operator*() const noexcept { return i; }
      constexpr bool operator!=(const itr x) const noexcept { return i != x.i; }
    };
    constexpr rep(const usize first, const usize last) noexcept
      : f(first), l(last) {}
    constexpr itr begin() const noexcept { return itr(f); }
    constexpr itr end() const noexcept { return itr(l); }
  };
  class revrep {
    const usize f, l;

  public:
    class itr {
      friend revrep;
      usize i;
      constexpr itr(usize x) noexcept : i(x) {}

    public:
      void operator++() noexcept { --i; }
      constexpr usize operator*() const noexcept { return i; }
      constexpr bool operator!=(const itr x) const noexcept { return i != x.i; }
    };
    constexpr revrep(usize first, usize last) noexcept : f(--first), l(--last) {}
    constexpr itr begin() const noexcept { return itr(l); }
    constexpr itr end() const noexcept { return itr(f); }
  };
  template <class T> using vec_alias = std::vector<T>;
  template <class T> auto md_vec(const usize n, const T& value) {
    return std::vector<T>(n, value);
  }
  template <class... Args> auto md_vec(const usize n, Args... args) {
    return std::vector<decltype(md_vec(args...))>(n, md_vec(args...));
  }
  template <class T> constexpr T difference(const T& a, const T& b) {
    return a < b ? b - a : a - b;
  }
  template <class T> T scan() {
    T ret;
    std::cin >> ret;
    return ret;
  }

} // namespace n91

#include <algorithm>
#include <iostream>
#include <set>
#include <utility>
#include<numeric>

namespace n91 {

  void main_() {
    usize n = scan<usize>();
    std::vector<u64> p(n);
    for (auto& e : p) {
      std::cin >> e;
    }
    p.insert(p.begin(), n);
    p.insert(p.end(), n);
    std::multiset<usize> set{ 0_z, 0_z, n + 1_z, n + 1_z };
    std::vector<usize> idx(n);
    std::iota(idx.begin(), idx.end(), 1_z);
    std::sort(idx.begin(), idx.end(),
      [&p](const usize l, const usize r) { return p[r] < p[l]; });
    u64 ans = static_cast<u64>(0);
    for (const auto i : idx) {
      const auto it = set.insert(i);
      const auto ne = std::next(it);
      const auto nene = std::next(ne);
      const auto pr = std::prev(it);
      const auto prpr = std::prev(pr);
      ans += p[i] * static_cast<u64>(*pr - *prpr) * static_cast<u64>(*ne - *it);
      ans += p[i] * static_cast<u64>(*it - *pr) * static_cast<u64>(*nene - *ne);
    }
    std::cout << ans << std::endl;
  }

} // namespace n91

int main() {
  n91::main_();
  return 0;
}


Measured memory_bytes: 6512