2295.cpp

// Authored by : BaaaaaaaaaaarkingDog
// Co-authored by : -
// http://boj.kr/f19cd7f505434920a0a4a9aa86454364
#include <bits/stdc++.h>
using namespace std;

int n;
int a[1005];
vector<int> two;

int main(void) {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cin >> n;
  for(int i = 0; i < n; i++) cin >> a[i];
  sort(a, a+n);
  for(int i = 0; i < n; i++){
    for(int j = i; j < n; j++)
      two.push_back(a[i]+a[j]);
  }
  sort(two.begin(), two.end());
  for(int i = n-1; i > 0; i--){
    for(int j = 0; j < i; j++){
      if(binary_search(two.begin(), two.end(), a[i]-a[j])){
        cout << a[i];
        return 0;
      }
    }
  }
}