#include <iostream>
#include <vector>
#include <numeric>
#include <algorithm>

using namespace std;

int main() {
  int n;
  vector<int> datas;
  vector<int> sums;

  while (cin >> n, n != 0) {
    int input;
    for (int n_i = 0; n_i < n; n_i++) {
      cin >> input;
      datas.push_back(input);
    }
    for (int data_i = 0; data_i < n-1; data_i++) {
      sums.push_back(datas[data_i]+datas[data_i]);
    }
    cout << *max_element(sums.begin(), sums.end()) << endl;
  }

  return 0;
}