#include <iostream>
#include <fstream>

using namespace std;
ifstream fin ("pinguini.in");
ofstream fout ("pinguini.out");
int v[10001], n, k;
int c;

int main()
{
    fin >> c >> n;
    if (c == 1)
    {
        for (int i = 1; i<=n; i++)
            fin >> v[i];
        for (int i = 1; i<=n; i++)
            if (v[i] == 2)
                k++;
        fout << k;
    }
    if (c == 2)
    {
        for (int i = 1; i<=n; i++)
            fin >> v[i];
        for (int i = 1; i<n; i++)
            if (v[i] == 2 and v[i+1] == 1)
                k++;
        if (v[n] == 2)
            k++;
        fout << k;
    }
    if (c == 3)
    {
        int kmax = 0;
        for (int i = 1; i<=n; i++)
            fin >> v[i];
        for (int i = 1; i<=n; i++)
            if (v[i] == 2)
            {
                k++;
                if (k > kmax)
                    kmax = k;
            }
            else
            k = 0;
        fout << kmax;

    }
    return 0;
}