#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
#define rrep(ri,n) for(int ri = (int)(n-1); ri >= 0; ri--)
#define rep2(i,x,n) for(int i = (int)(x); i < (int)(n); i++)
#define repit(itr,x) for(auto itr = x.begin(); itr != x.end(); itr++)
#define rrepit(ritr,x) for(auto ritr = x.rbegin(); ritr != x.rend(); ritr++)
#define ALL(x) x.begin(), x.end()
using ll = long long;
using namespace std;

int main(){
  int n;
  cin >> n;
  vector<pair<int, int>> p(n);
  rep(i, n){
    int in;
    cin >> in;
    p.at(i) = make_pair(in, i);
  }
  sort(p.begin(), p.end());
  list<pair<int, int>> list;
  list.push_back(p.front()); list.push_back(p.at(1));
  bool mode = list.front().second < list.back().second;
  rep2(i, 2, n){
    int l = min(list.front().second, list.back().second);
    int r = max(list.front().second, list.back().second);
    if(l < p.at(i).second && p.at(i).second < r){
      for(auto q : list){
        if(mode == true){
          if(q.second > p.at(i).second){
            cout << q.first + p.at(i).first + list.front().first << endl;
            return 0;
          }
        }else{
          if(q.second < p.at(i).second){
            cout << q.first + p.at(i).first + list.front().first << endl;
            return 0;
          }
        }
      }
      return 0;
    }
    list.push_back(p.at(i));
  }
  cout << -1 << endl;
  return 0;
}