#include <cstdio>
#include <stdint.h>
#include <iostream>
#include <cstring>
#include <cmath>
#include <vector>
#include <string>
#include <utility>
using namespace std;

const int EMPTY = 0, WHITE = 1, BLACK = 2;

int total_black;
int tab[20][20], n, m;
int dirs[][2] = {
    {1, -1}, // NW
    {1, 1},  // NE
    {-1, -1}, // SW
    {-1, 1} // SE
};

int black_map[70], reverse_black_map[200];

int bt(uint64_t v, int i, int j) {
    vector<pair<int, int> > neigh;
    int ii, jj;

    for (int d = 0; d < 4; d++) {

        ii = i + dirs[d][0];
        jj = j + dirs[d][1];
        while (ii >= 0 && ii < n && jj >= 0 && jj < m && !tab[ii][jj]) {
            ii += dirs[d][0];
            jj += dirs[d][1];
        }
        if (ii >= 0 && ii < n && jj >= 0 && jj < m) {
            if (tab[ii][jj] == BLACK) {
                neigh.push_back(make_pair(d, ii * m + jj));
            }
        }
    }

    int mx = __builtin_popcount((uint32_t) v) + __builtin_popcount(v >> 32);
    uint64_t vv = v;
    for (int k = 0; k < neigh.size(); k++) {
        // se já visitou...
        int id = reverse_black_map[neigh[k].second];
        uint64_t neigh_mask = 1 << id;
        if (neigh_mask & v) continue;

        vv  = v | neigh_mask;

        // Essa é a posição após capturar a peça
        int d = neigh[k].first;
        ii = neigh[k].second / m + dirs[d][0];
        jj = neigh[k].second % m + dirs[d][1];

        //cout << "capturou e caiu em " << ii << " " << jj << endl;

        while (ii >= 0 && ii < n && jj >= 0 && jj < m && !tab[ii][jj]) {
            //cout << "... e sair de " << ii << " " << jj << endl;
            int tmp = bt(vv, ii, jj);
            if (tmp > mx) mx = tmp;

            ii += dirs[d][0];
            jj += dirs[d][1];
        }
    }
    return mx;
}

int main() {
    for (;;) {
        scanf("%d %d", &n, &m);
        if (n == 0 && m == 0) break;
        memset(tab, 0, sizeof(tab));
        memset(black_map, 0, sizeof(black_map));
        memset(reverse_black_map, -1, sizeof(reverse_black_map));
        total_black = 0;

        for (int i = 0; i < n * m; i += 2) {
            int ii = i / m;
            int jj = i % m;
            if (m % 2 == 0) jj += ii & 1;
            scanf("%d", &tab[ii][jj]);
            if (tab[ii][jj] == BLACK) {
                black_map[total_black] = ii * m + jj;
                reverse_black_map[black_map[total_black]] = total_black;
                total_black++;
            }
        }
        int mx = 0;
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; j++) {
                if (tab[i][j] == WHITE) {
                    //cout << "-->saindo de " << i << " " << j << endl;
                    mx = max(mx, bt(0, i, j));
                }
            }
        }
        printf("%d\n", mx);
    }
    return 0;
}