#include <bits/stdc++.h>
using namespace std;
#pragma comment(linker, "/stack:200000000")
#pragma GCC optimize("O3")
#pragma GCC optimize("O2")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
template <typename T>
ostream& operator<<(ostream& os, const vector<T>& v) {
  for (long long i = 0; i < v.size(); ++i) os << v[i] << " ";
  return os;
}
template <typename T>
ostream& operator<<(ostream& os, const set<T>& v) {
  for (auto it : v) os << it << " ";
  return os;
}
template <typename T, typename S>
ostream& operator<<(ostream& os, const pair<T, S>& v) {
  os << v.first << " " << v.second;
  return os;
}
const long long mod = 1e9 + 7;
const long long inf = 2e18;
const long long ninf = -2e18;
long long pow(long long a, long long b, long long m) {
  long long ans = 1;
  while (b) {
    if (b & 1) ans = (ans * a) % m;
    b /= 2;
    a = (a * a) % m;
  }
  return ans;
}
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  time_t t1, t2;
  t1 = clock();
  long long n;
  cin >> n;
  set<long long> s;
  long long rsum = 0;
  long long arr[n];
  for (long long i = 0; i < n; i++) {
    long long x;
    cin >> arr[i];
    rsum += arr[i];
    s.insert(rsum);
  }
  long long s2 = 0;
  long long ans = 0;
  for (long long i = n - 1; i >= 0; i--) {
    s.erase(rsum);
    rsum -= arr[i];
    s2 += arr[i];
    if (s.find(s2) != s.end()) {
      ans = max(ans, s2);
    }
  }
  cout << ans << '\n';
  t2 = clock();
  cerr << '\n' << t2 - t1 << '\n';
  return 0;
}
