#include <bits/stdc++.h>
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define printVec(v) printf("{"); for (const auto& i : v) { std::cout << i << ", "; } printf("}\n");
#define ALL(obj) (obj).begin(), (obj).end()
#define debug(x) cout << #x << ": " << x << '\n';
#define degreeToRadian(deg) (((deg)/360)*2*M_PI)
#define radianTodegree(rad) (((rad)/2/M_PI)*360)
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
using namespace std;
using P = pair<int,int>;
using ll = long long;
const ll INF = 1LL<<60;
const int MOD = 1e9 + 7;
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};

//cin.tie(0);ios::sync_with_stdio(false);
//cout << fixed << setprecision(15) << y << endl;
int main() {
  int N;
  cin >> N;
  cin.ignore();
  vector<ll> A;

  for (int i = 0; i < N; i++) {
    string s; getline(cin, s);
    if (s.find(' ') != string::npos) {
      cout << "assert" << endl;
    } else {
      A.push_back(s[0] - '0');
    }
  }

  set<ll> st;
  for (int i = 0 ; i < N; i++) {
    for (int j = i + 1; j < N; j++) {
      st.insert(A[i] + A[j]);
    }
  }

  cout << *(++st.rbegin()) << endl;
  
  return 0;
}