#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

int main()
{
    int n;
    scanf("%d", &n);

    vector<pair<long, int>> va;

    for (int i = 0; i < n; ++i)
    {
        long a;
        scanf("%ld", &a);
        va.push_back(make_pair(a, i));
    }

    sort(va.begin(), va.end());

    long tmin{ 300000001 };
    for (int i = 0; i < n - 1; ++i)
    {
        if (va[i].second > n - 2)
            continue;
        for (int j = i + 1; j < n; ++j)
        {
            if (va[i].second > va[j].second)
                continue;
            if (va[i].first + va[j].first > tmin)
                break;
            for (int k = 0; k < j; ++k)
            {
                if (k == i)
                    continue;
                if (va[j].second > va[k].second)
                        continue;
                if (va[i].first + va[j].first + va[k].first > tmin)
                    break;
                tmin = min(va[i].first + va[j].first + va[k].first, tmin);
            }
        }
    }

    if (tmin == 300000001)
        printf("-1\n");
    else
        printf("%ld\n", tmin);

    return 0;
}