#pragma GCC optimize ("O3")

#include <bits/stdc++.h>

using namespace std;

#ifdef LOCAL
#include <prettyprint.hpp>
#define debug(...)  cerr << "[" << #__VA_ARGS__ << "]: ", d_err(__VA_ARGS__);
#else
#define debug(...) 83;
#endif

void d_err() {
    cerr << endl;
}

template <typename H, typename... T>
void d_err(H h, T... t) {
    cerr << h << " ";
    d_err(t...);
}

template <typename T>
void print(T x) {
    cout << x << endl;
}

#define ALL(x) (x).begin(), (x).end()
#define FOR(i, m, n) for (int i = (m); i < (n); ++i)
#define REVFOR(i, m, n) for (int i = (n - 1); i >= (m); --i)
#define REP(i, n) FOR(i, 0, n)
#define REVREP(i, n) REVFOR(i, 0, n)
#define fi first
#define se second
#define pb push_back
#define mp make_pair
#define eb emplace_back
#define bcnt __builtin_popcountll

typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef pair<ll,ll> Pll;
typedef pair<int,int> Pin;

ll INF = 1e16;
int inf = 1e9;
ll MOD = 1e9+7;

int main(){
    cin.tie(0);
    ios_base::sync_with_stdio(false);
    cout << fixed << setprecision(20);
    
    int N;
    cin >> N;

    vector<int> A(N);
    REP(i, N) cin >> A[i];

    multiset<int> l, r;
    REP(i, N) r.insert(A[i]);

    ll ans = INF;
    REP(i, N) {
        ll b = A[i];

        r.erase(b);
        if (!l.empty() && !r.empty()) {
            // large
            auto a = *l.begin();
            auto c = *r.begin();
            if (a < b && c < b) ans = min(ans, a + b + c);

            // small
            auto a_it = l.lower_bound(b);
            auto c_it = r.lower_bound(b);

            if (a_it != l.end() && c_it != r.end()) {
                ans = min(ans, *a_it + b + *c_it);
            }
        }

        l.insert(b);
    }

    if (ans == INF) print(-1);
    else print(ans);
    
}