foto

#include <fstream>

using namespace std;

ifstream fin("foto.in");
ofstream fout("foto.out");

struct foto
{
    int l, c;
};

int F[102][102], N, M, i, j;

int fill(int i, int j)
{
    foto C[10010], X;
    int ic, sc, dir, l9, c9;
    int dl[] = {0, -1, 0, 1, 0};
    int dc[] = {0, 0, 1, 0, -1};
    int nr = 0;
    F[i][j] = 2; nr++;
    ic = 0; sc = 0;
    C[sc].l = i; C[sc].c = j;
    while (ic <= sc)
    {
        X = C[ic++];
        for (dir = 1; dir <= 4; dir++)
        {
            l9 = X.l + dl[dir];
            c9 = X.c + dc[dir];
            if (F[l9][c9] == 0)
            {
                F[l9][c9] = 2; nr++;
                sc++; C[sc].l = l9; C[sc].c = c9;
            }
        }
    }
    return nr;
}

void citire()
{
    int i, j;
    fin >> N >> M;
    for (i = 1; i <= N; i++)
        for (j = 1; j <= M; j++)
            fin >> F[i][j];
}

void bordare()
{
    int i;
    for (i = 0; i <= N+1; i++)
        F[i][0] = F[i][M+1] = 1;
    for (i = 0; i <= M+1; i++)
        F[0][i] = F[N+1][i] = 1;
}

int main()
{
    int i, j, cate, cateMAX = 0;
    citire();
    bordare();
    for (i = 1; i <= N; i++)
        for (j = 1; j <= M; j++)
            if (F[i][j] == 0)  //am gasit o zona luminoasa
            {
                cate = fill(i, j);
                if (cate>cateMAX)
                    cateMAX = cate;
            }
    fout << cateMAX << '\n';
    return 0;
}