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

int main() {
  int n;
  cin>>n;
  string s;
  getline(cin, s);
  getline(cin, s);
  if (s.find(" ") != string::npos) {
    cout<<"\"assert\""<<endl;
    return 0;
  }
  long a[n];
  a[0] = stol(s);
  for (int i=1; i<n; i++) cin>>a[i];
  set<long> sum;
  for (int i=0; i<n; i++) {
    for (int j=i+1; j<n; j++) {
      sum.insert(a[i] + a[j]);
    }
  }
  vector<int> vs(sum.begin(), sum.end());
  reverse(vs.begin(), vs.end());
  cout<<vs[1]<<endl;
}