/in/foo.cc: In function 'void BFS()':
/in/foo.cc:36:12: warning: unused variable 'now' [-Wunused-variable]
  int tx,ty,now;
            ^~~
/in/foo.cc: In function 'bool check(int, int, int, int)':
/in/foo.cc:29:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^