#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <iomanip>
#include <cmath>
#include <stdio.h>
#include <queue>
#include <deque>
#include <cstdio>
#include <set>
#include <map>
#include <bitset>
#include <stack>
#include <cctype>
using namespace std;
int a[200020];
int ml[200020], mr[200020];
int main() {
	int n;
	cin >> n;
	for (int i = 0; i < n; i++) {
		cin >> a[i];
	}
	int nl = 1000000007, nr = 1000000007;
	set<int> stl, str;
	for (int i = 0; i < n; i++) {
		if (nl > a[i]) {
			nl = a[i];
		}
		if (nr > a[n - i - 1]) {
			nr = a[n - i - 1];
		}
		ml[i] = nl;
		mr[n - i - 1] = nr;
		if (i > 1) {
			str.insert(a[i]);
		}
	}
	stl.insert(a[0]);
	int ans = 1000000007;
	for (int i = 1; i < n - 1; i++) {
		bool bo = true, bo1 = true;
		if (a[i] <= ml[i - 1] || a[i] <= mr[i + 1]) {
			bo = false;
		}
		auto itr = stl.set::upper_bound(a[i]);
		auto itr1 = str.set::upper_bound(a[i]);
		if (itr == stl.end() || itr1 == str.end()) {
			bo1 = false;
		}
		if (bo) {
			if (ans > ml[i - 1] + a[i] + mr[i + 1]) {
				ans = ml[i - 1] + a[i] + mr[i + 1];
			}
		}
		if (bo1) {
			if (ans > *itr + a[i] + *itr1) {
				ans = *itr + a[i] + *itr1;
			}
		}
		str.erase(a[i + 1]);
		stl.insert(a[i]);
	}
	if (ans == 1000000007) {
		cout << "-1" << endl;
		return 0;
	}
	cout << ans << endl;
}