#include<iostream>
using namespace std;
int main() {
	int N, V[1000];
	int max;
	int maxDouble = 0;
	cin >> N;
	for (int i = 0; i < N; i++) {
		cin >> V[i];
	}
	if (N <= 2) {
		for (int i = 0; i < N; i++) {
			if (maxDouble < V[i]) maxDouble = V[i];
		}
	}
	else if (N == 3) {
		if (V[0] + V[2] > V[1]) {
			maxDouble = V[0] + V[2];
		}
		else {
			maxDouble = V[1];
		}
	}
	else {
		for (int i = 0; i < N - 2; i++) {
			max = 0;
			for (int j = i + 2; j < N; j++) {
				if (V[j] > max) max = V[j];
			}
			if (max + V[i] > maxDouble)maxDouble = max + V[i];
		}
	}
	cout << maxDouble << endl;
}