#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++)
{
    if(masyvas[i] == 0) {
        ++ats;
        if (ats > max) {
            max = ats;
        }
    }
    else
    {
        ats = 0;
    }
}

  if(max == 0 )
{
    cout<<"No"<<endl;
}
else
{
cout << max << endl;
}
}