/in/foo.cc: In function 'int main()':
/in/foo.cc:38:12: warning: 'ty' may be used uninitialized in this function [-Wmaybe-uninitialized]
  dfs(tx,ty);
            ^
/in/foo.cc:38:12: warning: 'tx' may be used uninitialized in this function [-Wmaybe-uninitialized]