#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  long long arr[n];
  for (int i = 0; i < n; i++) scanf("%lld", &arr[i]);
  map<long long, int> mp;
  long long sum = 0;
  for (int i = n - 1; i >= 0; i--) {
    sum += arr[i];
    mp[sum] = i;
  }
  long long ans = 0;
  long long cnt = 0;
  for (int i = 0; i < n; i++) {
    cnt += arr[i];
    if (mp[cnt] > i && mp[cnt] != 0) {
      ans = max(cnt, ans);
    }
  }
  cout << ans << endl;
}
