#include <iostream>
#include <vector>

using namespace std;

int ivice(vector<vector<int>> &mat, int i, int j) {
    if(i < 0 || j < 0 || i >= mat.size() || j >= mat[0].size()) return 1;
    if(mat[i][j] == 0) return 1;
    if(mat[i][j] == 2) return 0;

    mat[i][j] = 2;

    int o = ivice(mat, i+1, j);
    o += ivice(mat, i, j+1);
    o += ivice(mat, i-1, j);
    o += ivice(mat, i, j-1);
    return o;
}

int main() {
    int n, m;
    cin >> n >> m;

    vector<vector<int>> mat(n, vector<int>(m));
    for(int i = 0; i < n; i++) {
        for(int j = 0; j < m; j++) {
            cin >> mat[i][j];
        }
    }

    // 0 - voda
    // 1 - kopno
    // 2 - obidjeno
    int obim = 0;
    for(int i = 0; i < n; i++) {
        for(int j = 0; j < m; j++) {
            if(mat[i][j] == 1) {
                int rez = ivice(mat, i, j);
                if(rez > obim) obim = rez;
            }
        }
    }

    cout << obim << endl;
}