vector<int> S = {-1, 0, 1};

void component(int i, int j, int n, int m, const vector<vector<int>>& grid, vector<vector<bool>>& visited, int& size) {
    visited[i][j] = true;
    ++size;
    for (int I : S) {
        for (int J : S) {
            if (i+I < 0 or i+I >= n or j+J < 0 or j+J >= m or visited[i+I][j+J] or grid[i+I][j+J] == 0) continue;
            component(i+I, j+J, n, m, grid, visited, size);
        }
    }
}

int maxRegion(int n, int m, const vector<vector<int>>& grid) {
    vector<int> components;
    vector<vector<bool>> visited(n, vector<bool>(m));
    int size = 0;
    for (int i=0; i < n; ++i) {
        for (int j=0; j < m; ++j) {
            if (visited[i][j] or grid[i][j] == 0) continue;
            size = 0;
            component(i, j, n, m, grid, visited, size);
            components.push_back(size);
        }
    }
    return *max_element(components.begin(), components.end());
}

int main()
{
    int n, m, k;
    cin >> n >> m;
    vector<vector<int>> grid(n, vector<int>(m));
    for (int i=0; i < n; ++i) {
        for (int j=0; j < m; ++j) {
            cin >> k;
            grid[i][j] = k;
        }
    }
    cout << maxRegion(n, m, grid);
}