#include <iostream>
#include <fstream>
#include <string>
#include <algorithm>
using namespace std;

int main() {
	int n;
	//C:\Users\misha\Desktop\2281.txt
	string st;
	//string line;
	cin >> st;
	fstream in;
	in.open(st, ios::in);
	//long long int* s = new long long int;
	//long long int a[4];
	//long long int* s = new long long int[1001];
//	string* input = new string[1001];
	in >> n;
	long long int* s = new long long int[n];
	//long long int  i = 0;
	for(long long int i = 0; i < n; ++i) {
		in >> s[i];
	}
	in.close();
	//cout << i << endl;
	long long int ma = -2281337228;
	for (long long int j = 0; j < n; ++j)
	{
			for (long long int q = 0; q < n; ++q)
			{
				if (abs(j - q) >= 4 && (s[j] + s[q]) % 2 == 0 && (s[j] + s[q]) > ma)
					ma = s[j] + s[q];
			}
	}
	if (ma != -2281337228)
		cout << ma;
	else
		cout << 0;
	//cout << endl;
//	cout << stoi("");
}
//0 1 2 3 4 5 6 7 8 9