#include<bits/stdc++.h>
using namespace std;
#define int long long
#define REP(i,m,n) for(int i=(m);i<(n);i++)
#define rep(i,n) REP(i,0,n)
#define pb push_back
#define all(a) a.begin(),a.end()
#define rall(c) (c).rbegin(),(c).rend()
#define mp make_pair
#define double long double
#define endl '\n'
typedef long long ll;
typedef pair<ll,ll> pll;
const ll inf=1e9+7;
const ll mod=1e9+7;
signed main(){
    ll n;cin>>n;
    vector<ll>a(n);
    rep(i,n)cin>>a[i];
    ll mi=inf;
    vector<ll>b(n,inf);
    vector<ll>c(n,inf);
    b[0]=a[0];
    REP(i,1,n){
        b[i]=min(b[i-1],a[i]);
    }
    c[n-1]=a[n-1];
    for(int i=n-2;i>=0;i--){
        c[i]=min(c[i+1],a[i]);
    }
    REP(i,1,n-1){
        if(a[i]>b[i-1]&&a[i]>c[i+1]){
            mi=min(mi,a[i]+b[i-1]+c[i+1]);
        }
    }
    set<ll>s,t;
    rep(i,n){
        t.insert(a[i]);
    }
    t.erase(a[0]);
    t.erase(a[1]);
    s.insert(a[0]);
    REP(i,1,n-1){
        auto itr1=s.upper_bound(a[i]);
        auto itr2=t.upper_bound(a[i]);
        if(itr1!=s.end()&&itr2!=t.end()){
            mi=min(a[i]+*itr1+*itr2,mi);
        }
        s.insert(a[i]);
        t.erase(a[i+1]);
    }
    if(mi==inf)cout<<-1<<endl;
    else cout<<mi<<endl;
}