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

#define rep(i, n) for(int i=0, i##_len=(n); i<i##_len; ++i)
#define reps(i, n) for(int i=1, i##_len=(n); i<=i##_len; ++i)
#define rrep(i, n) for(int i=((int)(n)-1); i>=0; --i)
#define rreps(i, n) for(int i=((int)(n)); i>0; --i)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define sz(x) ((int)(x).size())
#define pl(s) cout << (s) << "\n";
#define pls(...) {bool space = false; for(auto i : __VA_ARGS__) (cout << (space?" ":"") << i), space = true; cout << "\n";}
#define plexit(s) {cout << (s) << "\n"; exit(0);}
#define yes(s) cout << ((s)?"Yes":"No") << "\n";
#define pb push_back
#define pcnt __builtin_popcountll

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

#ifdef __LOCAL
#include <dump.hpp>
#define dump(...)                                                            \
  DUMPOUT << "  " << string(#__VA_ARGS__) << ": "                            \
          << "[" << to_string(__LINE__) << ":" << __FUNCTION__ << "]"        \
          << endl                                                            \
          << "    ",                                                         \
      dump_func(__VA_ARGS__)
#else
#define dump(...)
#endif

struct IOInit {
  static constexpr int IOS_PREC = 15;
  static constexpr bool AUTOFLUSH = false;

  IOInit() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(IOS_PREC);
    dump(IOS_PREC);
    if(AUTOFLUSH) cout << unitbuf;
  }
} IO_INIT;

using i64 = std::int_fast64_t;
using i128 = __int128_t;
using ll = long long;
using ull = unsigned long long;
using ld = long double;
using pii = std::pair<int, int>;
using pll = std::pair<ll, ll>;
using vi = std::vector<int>;
using vvi = std::vector<vector<int>>;
using vl = std::vector<ll>;
using vp = std::vector<pii>;

constexpr int INFINT = (1 << 30) - 1;                    // 1.07x10^ 9
constexpr int INFINT_LIM = (1LL << 31) - 1;              // 2.15x10^ 9
constexpr ll INFLL = 1LL << 60;                          // 1.15x10^18
constexpr ll INFLL_LIM = (1LL << 62) - 1 + (1LL << 62);  // 9.22x10^18
constexpr ld eps = 1e-6;
constexpr ll MOD = 1000000007;
constexpr ld PI = 3.141592653589793238462643383279;
constexpr int dx4[4] = {1, 0, -1, 0};
constexpr int dy4[4] = {0, 1, 0, -1};
constexpr int dx8[8] = {1, 0, -1, 0, 1, -1, -1, 1};
constexpr int dy8[8] = {0, 1, 0, -1, 1, 1, -1, -1};


signed main(void) {
  int N; cin >> N;
  vl A(N); rep(i,N) cin >> A[i];
  ll ans = INFLL;
  bool ok = false;

  vector<bool> visited(N);
  auto dfs = [&](auto && dfs, int v, vl t) -> void {
    if (v == N) {
      if (t.size()<3) return;
      ll a = t[0];
      ll b = t[1];
      ll c = t[2];
      if (max({a,b,c}) == b || min({a,b,c}) == b) {
        if (a != b && b != c && c != a) {
          chmin(ans,a+b+c); //dump(ans,a,b,c);
          ok = true;
        }
      }
      return;
    }

    if (t.size()<3) {
      t.pb(A[v]);
      dfs(dfs,v+1,t);
      t.pop_back();
    }
    dfs(dfs,v+1,t);
  };
  dfs(dfs,0,{});

  // int k = 3;
  // int x, y;
  // for (int bit = (1 << k) - 1; bit < (1 << N); x = bit & -bit, y = bit + x, bit = (((bit & ~y) / x) >> 1) | y)  {
  //   vl t;
  //   rep(i,N) {
  //     if (bit&(1 << i)) t.pb(A[i]);
  //   }
  //   ll a = t[0];
  //   ll b = t[1];
  //   ll c = t[2];
  //   if (max({a,b,c}) != b && min({a,b,c}) != b){
  //     continue;
  //   }
  //   if (a != b && b != c && c != a) {
  //     if(chmin(ans,a+b+c)) dump(ans,a,b,c);
  //     ok = true;
  //   }
  // }

  if (!ok) plexit("-1")
  pl(ans)
  return 0;
}