#include<bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef vector<ll> vll;
typedef vector<vector<ll>> vvll;
typedef vector<vector<vector<ll>>> vvvll;
typedef vector<bool> vb;
typedef vector<vector<bool>> vvb;
typedef vector<vector<vector<bool>>> vvvb;
typedef pair<ll, ll> pll;
typedef vector<pll> vpll;
typedef vector<vpll> vvpll;
typedef vector<double> vd;
typedef vector<vd> vdd;

typedef pair<double, double> pd;
typedef vector<pd> vpd;


#define FOR(i,x,y) for(ll i=(ll)x; i<(ll)y; ++i)
#define REP(i,y) FOR(i, 0, y)
#define RFOR(i,x,y) for(ll i=(ll)x; i>=(ll)y; --i)
#define RREP(i,x) RFOR(i, x, 0)
#define ALL(a) a.begin(), a.end()
#define pb push_back
#define debug_print(x...) cerr << "line " << __LINE__ << " : "; debug_print_in(x);

template <typename First>
void debug_print_in(First first){
  cerr << first << endl;
  return;
}

template <typename First, typename... Rest>
void debug_print_in(First first, Rest... rest){
  cerr << first << " ";
  debug_print_in(rest...);
  return;
}

void IN(void){
  return;
}

template <typename First, typename... Rest>
void IN(First& first, Rest&... rest){
  cin >> first;
  IN(rest...);
  return;
}

template <typename First>
void OUT(First first){
  cout << first << endl;
  return;
}

template <typename First, typename... Rest>
void OUT(First first, Rest... rest){
  cout << first << " ";
  OUT(rest...);
  return;
}

template<class t, class u> t chmax(t&a,u b){if(a<b)a=b; return a;};
template<class t, class u> t chmin(t&a,u b){if(a>b)a=b; return a;};
int popcount(int t){return __builtin_popcount(t);} //GCC
int popcount(ll t){return __builtin_popcountll(t);} //GCC

template <typename T>
void vec_print(vector<T> VEC){
  REP(i, VEC.size()){
    cerr << VEC[i] << " ";
  }
  cerr << endl;
};

template <typename T>
void mat_print(vector<vector<T> > MAT){
  REP(i,MAT.size()){
    REP(j,MAT[i].size()){
      cerr << MAT[i][j] << " ";
    }
    cerr << endl;
  }
};

constexpr int INF = (1<<30);
constexpr ll INFLL = 1LL<<62;
constexpr long double EPS = 1e-12;
constexpr ll MOD = (ll)((1E+9)+7);

int main(){
  cin.tie(0); // cut the cin and cout (default, std::flush is performed after std::cin)
  ios::sync_with_stdio(false); // cut the iostream and stdio (DON'T endl; BUT "\n";)

  ll N;
  IN(N);
  vpll V(N);
  vll P(N);
  REP(i,N){
    IN(P[i]);
    V[i].first = P[i];
    V[i].second = i;
  }

  sort(ALL(V));
  reverse(ALL(V));

  vll F1(N, -1), F2(N, -1), B1(N, N), B2(N, N);

  set<ll> st;

  REP(i,N){
    ll index = V[i].second;
    st.emplace(index);
    auto itr1 = st.find(index);
    auto itr2 = itr1;

    itr1++;
    if(itr1!=st.end()){
      B1[index]=*itr1;
      itr1++;
      if(itr1!=st.end()){
        B2[index]=*itr1;
      }
    }

    if(itr2!=st.begin()){
      itr2--;
      F1[index]=*itr2;
      if(itr2!=st.begin()){
        itr2--;
        F2[index]=*itr2;
      }
    }

    debug_print(V[i].first, V[i].second, F2[index], F1[index], B1[index], B2[index]);
  }

  ll ans = 0;

  REP(i,N){
    ll C = 0;
    C = (F1[i]-F2[i])*(B1[i]-i) + (B2[i]-B1[i])*(i-F1[i]);
    debug_print(i, F2[i], F1[i], B1[i], B2[i], C);
    ans += P[i] * C;
  }

  OUT(ans);

  return 0;
}

Measured memory_bytes: 10496