###--------------------------------------------------------------------------
### Imported modules.
-from sys import argv, stdin, stdout, stderr
+import sys as SYS; from sys import argv, stdin, stdout, stderr
import os as OS
import itertools as I
import math as M
import catacomb as C
+if SYS.version_info >= (3,):
+ xrange = range
+ range = lambda *args: list(xrange(*args))
+
###--------------------------------------------------------------------------
### Utilities.