/in/foo.cc: In function 'int query(int, int)':
/in/foo.cc:70:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  if (k < 0 && dn[x].size () <= -k) exit (0);
               ~~~~~~~~~~~~~~^~~~~
/in/foo.cc:71:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  if (k >= 0 && up[x].size () <= k) exit (0);
                ~~~~~~~~~~~~~~^~~~