#include <cstdio>
#include <cstring>
#include <iostream>
#include <string>
#include <cmath>
#include <bitset>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <algorithm>
#include <complex>
#include <unordered_map>
#include <unordered_set>
#include <random>
#include <cassert>
#include <fstream>
#include <utility>
#include <functional>
#include <time.h>
#include <stack>
#include <array>
#include <list>
#define popcount __builtin_popcount
using namespace std;
typedef long long int ll;
typedef pair<int, int> P;
const int INF=1e9+7;
int solve(int n, vector<int> a){
    int mnl[200020], mnr[200020];
    mnl[0]=INF, mnr[n]=INF;
    for(int i=0; i<n; i++){
        mnl[i+1]=min(mnl[i], a[i]);
    }
    for(int i=n-1; i>=0; i--){
        mnr[i]=min(mnr[i+1], a[i]);
    }
    int ans=INF;
    for(int i=0; i<n; i++){
        if(mnl[i]<a[i] && mnr[i+1]<a[i]) ans=min(ans, a[i]+mnl[i]+mnr[i+1]);
    }
    int t=min_element(a.begin(), a.end())-a.begin();
    ans=min(ans, a[t]+mnl[t]+mnr[t+1]);
    return ans;
}
int main()
{
    int n;
    cin>>n;
    vector<int> a(n);
    for(int i=0; i<n; i++) cin>>a[i];
    int ans=solve(n, a);
    if(ans>=INF) cout<<-1<<endl;
    else cout<<ans<<endl;
    return 0;
}