/in/foo.cc: In function 'void bfs(int, int, int, int)':
/in/foo.cc:19:7: warning: statement has no effect [-Wunused-value]
  check==0;
  ~~~~~^~~
/in/foo.cc:21:16: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
     if (check=0)
                ^