#include <bits/stdc++.h>
using namespace std;

long long n, a[1000001], b[100000];


int main() {
	cin >> n;
	for (long long i = 0; i < n; i++) {
		cin >> a[i];
		if (a[i] % 2 != 0) {
			i--;
			n--;
		}
	}
	sort(a, a + n);
	if (n == 0 || n == 1) {
		cout << -1;
	} else {
		cout << a[n - 1] + a[n - 2];
	}
	return 0;
}