Merged in DR v1.0.0.2

Utils.py

@@ -1,12 +1,11 @@
 #!/usr/bin/env python3
 import os
 import re
-import operator as op
 import subprocess
 import sys
 import xml.etree.ElementTree as ET
 from collections import defaultdict
-from functools import reduce
+from math import factorial
 from itertools import count
 
 
@@ -133,12 +132,9 @@ def kth_combination(k, l, r):
 
 
 def ncr(n, r):
-    if r == 0:
+    if r == 0 or r >= n:
         return 1
-    r = min(r, n-r)
-    numerator = reduce(op.mul, range(n, n-r, -1), 1)
-    denominator = reduce(op.mul, range(1, r+1), 1)
-    return numerator / denominator
+    return factorial(n) // factorial(r) // factorial(n-r)
 
 
 entrance_offsets = {