#include <bits/stdc++.h>
inline bool EQ(double a, double b) { return fabs(a - b) < 1e-9; }
const int INF = 1 << 29;
inline int two(int n) { return 1 << n; }
inline int test(int n, int b) { return (n >> b) & 1; }
inline void set_bit(int &n, int b) { n |= two(b); }
inline void unset_bit(int &n, int b) { n &= ~two(b); }
inline int last_bit(int n) { return n & (-n); }
inline int ones(int n) {
  int res = 0;
  while (n && ++res) n -= n & (-n);
  return res;
}
template <class T>
void chmax(T &a, const T &b) {
  a = max(a, b);
}
template <class T>
void chmin(T &a, const T &b) {
  a = min(a, b);
}
long long int gcd(long long int a, long long int b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
long long int lcm(long long int a, long long int b) {
  return (a * b) / gcd(a, b);
}
long long int max(long long int a, long long int b) {
  if (a > b) return a;
  return b;
}
long long int power(long long int x, long long int y) {
  long long int res = 1;
  while (y > 0) {
    if (y & 1) res = res * x;
    y = y >> 1;
    x = x * x;
  }
  return res;
}
long long int powermod(long long int x, long long int y) {
  long long int res = 1;
  x = x % 1000000007;
  while (y > 0) {
    if (y & 1) res = (res * x) % 1000000007;
    y = y >> 1;
    x = (x * x) % 1000000007;
  }
  return res;
}
int maxSubArraySum(int a[], int size) {
  int max_so_far = INT_MIN, max_ending_here = 0;
  for (int i = 0; i < size; i++) {
    max_ending_here = max_ending_here + a[i];
    if (max_so_far < max_ending_here) max_so_far = max_ending_here;
    if (max_ending_here < 0) max_ending_here = 0;
  }
  return max_so_far;
}
long long mulmod(long long a, long long b) {
  long long res = 0;
  a %= 1000000007;
  while (b) {
    if (b & 1) res = (res + a) % 1000000007;
    a = (2 * a) % 1000000007;
    b >>= 1;
  }
  return res;
}
bool isPrime(long long int n) {
  if (n <= 1) return false;
  if (n <= 3) return true;
  if (n % 2 == 0 || n % 3 == 0) return false;
  for (int i = 5; i * i <= n; i += 6) {
    if ((n % i == 0) || (n % (i + 2) == 0)) return false;
  }
  return true;
}
long double dist(long long int x1, long long int y1, long long int x2,
                 long long int y2) {
  return (long double)sqrt(
      (long double)((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2)));
}
long long int squaredist(long long int x1, long long int y1, long long int x2,
                         long long int y2) {
  return ((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
}
long long int nCr(long long int n, long long int r) {
  if (r == 0) return 1;
  return (n * nCr(n - 1, r - 1)) / r;
}
long long int countDivisors(long long int n) {
  long long int cnt = 0;
  for (int i = 1; i <= sqrt(n); i++) {
    if (n % i == 0) {
      if (n / i == i)
        cnt++;
      else
        cnt = cnt + 2;
    }
  }
  return cnt;
}
int xorRange(int x, int y) {
  if (x % 2 == 0) {
    int pattern[] = {y, 1, y + 1, 0};
    return pattern[(int)((y - x) % 4)];
  } else {
    int pattern[] = {x, x ^ y, x - 1, (x - 1) ^ y};
    return pattern[(int)((y - x) % 4)];
  }
}
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int n;
  cin >> n;
  vector<int> a(n);
  for (int i = 0; i < n; ++i) cin >> a[i];
  set<long long> sum;
  long long l = 0;
  for (int i = 0; i < n; ++i) {
    l += a[i];
    sum.insert(l);
  }
  long long ans = 0;
  long long r = 0;
  for (int i = n - 1; i >= 0; --i) {
    sum.erase(l);
    l -= a[i];
    r += a[i];
    if (sum.count(r)) ans = max(ans, r);
  }
  cout << ans << "\n";
  return 0;
}
