code1006C.cpp

/*
 * Contest : Codeforces
 * Problem : 1006C - Three Parts of the Array
 * Link    : https://codeforces.com/problemset/problem/1006/C
 */

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

#define fastio ios::sync_with_stdio(0); cin.tie(0);

int main() {
  fastio

  ll n; cin >> n;
  ll d[n];

  for (auto &e : d) cin >> e;

  ll l = 0, r = n - 1, ans = 0;
  ll sum1 = d[l], sum3 = d[r];
  while (l < r) {
    if (sum1 == sum3 && l < r) {
      ans = max(ans, sum1);

      l++;
      sum1 += d[l];
      r--;
      sum3 += d[r];
    }
    else if (sum1 < sum3) {
      l++;
      sum1 += d[l];
    }
    else {
      r--;
      sum3 += d[r];
    }
  }

  cout << ans << "\n";

  return 0;
}