#include <bits/stdc++.h>

using namespace std;
#define fast_io ios_base::sync_with_stdio(false), cin.tie(NULL), cout.tie(NULL)
#define pb push_back
#define int long long
#define ll long long
#define ld long double

#define rep(i, n) for (ll i=0; i<n; i++)
#define repi(i, n) for (ll i=1; i<=n; i++)

#define repi1(i, n) for (ll i = n; i >=0; i--)
#define mem(v, ha) memset(v, ha, sizeof(v))
#define all(a)  a.begin(), a.end()
#define allr(a)  a.rbegin(), a.rend()
#define CLOCK cerr << "\nTime elapsed: " << 1000 * clock() / CLOCKS_PER_SEC << "ms\n";
typedef vector<ll> vi;
typedef vector<vector<int>> vvi;
typedef vector<pair<ll, ll>> vpi;
typedef vector<char> vc;
#define no cout << "NO\n"
#define yes cout << "YES\n"
#define mp make_pair
#define ff first
#define ss second
const ll MOD = 1e9 + 7;
const ll mod = 998244353 ;

const long double PI = 3.141592653589793238460;
const int inf = (int)(1e9);

template<typename T> istream& operator>>(istream& in, vector<T>& a) {for (auto &x : a) in >> x; return in;};
template<typename T> ostream& operator<<(ostream& out, vector<T>& a) {for (auto &x : a) out << x << ' '; return out;};

// auto sum=[&](int use, int y){return use+y;};
// function <void(int)>dfs=[&](int u)  //void is the return type, int is the argument

void solve()
{
    int n;
    cin >> n;
    vi a(n);
    rep(i, n)
    cin >> a[i];
    vi dp1(n), dp2(n);
    int mini = a[0];
    dp1[0] = a[0];
    for (int i = 1; i < n; i++)
    {
        dp1[i] = dp1[i - 1];
        if (a[i] < mini)
        {
            mini = a[i];
            dp1[i] = mini;
        }
    }
    dp2[n - 1] = a[n - 1];
    mini = a[n - 1];
    for (int i = n - 2; i >= 0; i--)
    {   dp2[i] = dp2[i + 1];
        if (a[i] < mini)
        {
            mini = a[i];
            dp2[i] = mini;
        }

    }
    //for (auto l : dp1)
    //  cout << l << " ";
    int ans = INT_MAX;
    for (int i = 1; i < n - 1; i++)
    {
        int ml = dp1[i - 1];
        int ma = dp2[i + 1];
        if (a[i] > ml && a[i] > ma)
        {
            ans = min(ans, a[i] + ml + ma);
        }
    }


    vi dp3(n), dp4(n);



    int maxi = a[0];
    dp3[0] = a[0];
    for (int i = 1; i < n; i++)
    {
        dp3[i] = dp3[i - 1];
        if (a[i] < maxi)
        {
            maxi = a[i];
            dp3[i] = maxi;
        }
    }
    dp4[n - 1] = a[n - 1];
    maxi = a[n - 1];
    for (int i = n - 2; i >= 0; i--)
    {   dp4[i] = dp4[i + 1];
        if (a[i] < maxi)
        {
            maxi = a[i];
            dp4[i] = maxi;
        }

    }



    for (int i = 1; i < n - 1; i++)
    {
        int ml = dp3[i - 1];
        int ma = dp4[i + 1];
        if (a[i] < ml && a[i] < ma)
        {
            ans = min(ans, a[i] + ml + ma);
        }
    }




    if (ans == INT_MAX)
    {
        cout << -1 << '\n';
        return;
    }
    cout << ans << '\n';
}
int32_t main()
{


    fast_io;
    int T = 1;
   // cin >> T;

    while (T--)
    {
        solve();


    }

}