#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;
    }
}