#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<int> v(n);
  for (int i = 0; i < n; i++) cin >> v[i];
  int msf = v[0], mth = v[0];
  for (int i = 1; i < n; i++) {
    if (v[i] == 0) {
      mth = 0;
      continue;
    }
    mth += v[i];
    msf = max(msf, mth);
  }
  int i = 0;
  while (i < n) {
    if (v[i] == 0) break;
    mth += v[i];
    msf = max(msf, mth);
    i++;
  }
  cout << msf;
}
