/in/foo.cc: In function 'void bfs()':
/in/foo.cc:44:55: warning: suggest parentheses around comparison in operand of '|' [-Wparentheses]
                 if (nx < 0 || ny < 0 || nx >= m || ny >= n | a[nx][ny] == 'X') break;
                                                    ~~~^~~~
/in/foo.cc:53:31: warning: suggest parentheses around comparison in operand of '&' [-Wparentheses]
             if (nx >= 0 && ny >= 0 & nx < m && ny < n && a[nx][ny] != 'X' && !vis[nx][ny]) {
                            ~~~^~~~