#include <iostream>
using namespace std;
int a[101];
int main() {
    int n;
    cin >> n;
    for (int i = 0; i < n; i++) cin >> a[i];

    int s = a[0] + a[1] + a[2];
    for (int i = 1; i < n - 2; i++) s = max(s, a[i] + a[i + 1] + a[i + 2]);
    cout << s << endl;
    return 0;
}