#include <bits/stdc++.h>
using namespace std;
///////////////////////////////////////////
const long long int INF = 1LL<<60;
const long long int Mod = 1000000007;
using ll = long long int; using ci = const int;
using vi = vector<int>;  using Vi = vector<long long int>;
using P = pair<int, int>;  using PLL = pair<ll, ll>;
using matrix = vector<vector<ll>>;
#define pb(x) push_back(x)
#define mp(x,y) make_pair(x,y)
#define all(x) (x).begin(),(x).end()
#define rp(i,N) for(ll i = 0; i < (ll)N; i++)
#define repi(i,a,b) for(ll i = ll(a); i < ll(b); ++i)
template<class T>bool chmax(T &former, const T &b) { if (former<b) { former=b; return true; } return false; }
template<class T>bool chmin(T &former, const T &b) { if (b<former) { former=b; return true; } return false; }
template<class T>T sqar(T x){ return x*x; }//sqrt(x)は平方根;
#define Sort(v) std::sort(v.begin(), v.end(), std::greater<decltype(v[0])>()) //降順でVをソート
#define p_queue(v) priority_queue<v, vector<v>, greater<v> >
template<class T> inline void princ(T x){cout<<x<<" ";}; 
template<class T> inline void print(T x){cout<<x<<"\n";};
template<class T> inline void Yes(T condition){ if(condition) cout << "Yes" << endl; else cout << "No" << endl; }
template<class T> inline void YES(T condition){ if(condition) cout << "YES" << endl; else cout << "NO" << endl; }
///////////////////////////////////////////////////////////////////////////////////

void solve(){
    int n;
    cin >> n;
    Vi a(n);
    rp(i,n) cin >> a.at(i);
    Vi mins1(n),mins2(n);
    mins1[0]=a[0];
    mins2[0]=a[n-1];
    repi(i,1,n){
        mins1[i]=min(mins1[i-1],a[i]);
        mins2[i]=min(mins2[i-1],a[n-i-1]);
    }
    ll ans=INF;
    repi(i,1,n-1){
        if(a[i]>mins1[i-1]&&a[i]>mins2[n-i-2])
        chmin(ans,a[i]+mins1[i-1]+mins2[n-i-2]);
    }
    ll pos=1,midmin=INF;
    repi(i,1,n-1){
        if(chmin(midmin,a[i])) pos=i;
    }
    ll min1=INF,min2=INF;
    rp(i,pos){
        if(a[i]>a[pos]){
            chmin(min1,a[i]);
        }
    }
    repi(i,pos+1,n){
        if(a[i]>a[pos])
        chmin(min2,a[i]);
    }
    if(min1<INF&&min2<INF){
        chmin(ans,min1+min2+a[pos]);
    }
    if(ans>INF-10) print(-1);
    else print(ans);
    return;
}
int main(){
    cin.tie(0);ios::sync_with_stdio(false);
    std::cout<<std::fixed<<std::setprecision(30);
    solve();
    return 0;
}