#include <iostream>
#include <iomanip>
#include <string>
using namespace std;
int main()
{
  int n, masyvas[100], ats = 0, max = 0;
  cin >> n;
  for(int i = 0; i < n; i++)
    cin >> masyvas[i];
  for(int i=0;i<n;i++)
    masyvas[i] == 0 ? ++ats, (ats > max ? max = ats : NULL) : ats = 0;
  max == 0 ? cout << "No" << endl : cout << max << endl;
}