#include <bits/stdc++.h>
#define rep(i,n) for(ll i=0;i<(int)(n);i++)
using namespace std;
using ll = long long ;
using P = pair<int,int> ;
using pll = pair<long long,long long>;
constexpr int INF = 1e9;
constexpr long long LINF = 1e17;
constexpr int MOD = 1000000007;
constexpr double PI = 3.14159265358979323846;

int main(){
    int n;
    scanf("%d",&n);
    vector<ll> a(n);
    rep(i,n) scanf("%d",&a[i]);
    vector<ll> minl(n),minr(n);
    ll mn = INF;
    rep(i,n){
        minl[i] = mn;
        mn = min(mn,a[i]);
    }
    mn = INF;
    for(ll i=n-1;i>=0;i--){
        minr[i] = mn;
        mn = min(mn,a[i]);
    }
    ll ans = INF;
    rep(i,n){
        if(a[i] > minl[i] && a[i] > minr[i]){
            ans = min(ans,a[i] + minr[i] + minl[i]);
        }
    }
    vector<ll> maxr(n,-1),maxl(n,-1);
    set<ll> stl;
    rep(i,n){
        auto it = stl.upper_bound(a[i]);
        if(it!=stl.end()) maxl[i] = (*it);
        stl.insert(a[i]);
    }
    set<ll> str;
    for(ll i=n-1;i>=0;i--){
        auto it = str.upper_bound(a[i]);
        if(it!=str.end()) maxr[i] = (*it);
        str.insert(a[i]);
    }
    rep(i,n){
        if(a[i] < maxl[i] && a[i] < maxr[i]){
            ans = min(ans,a[i] + maxr[i] + maxl[i]);
        }
    }

    if(ans==LINF) cout << -1 << endl;
    else cout << ans << endl;
    return 0;
}