Improve item combination algorithm

src/Dodge/Data/ItemAmount.hs

@@ -0,0 +1,7 @@
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+module Dodge.Data.ItemAmount where
+
+newtype IcAmount = IcAmount {_toInt :: Int}
+  deriving (Eq,Ord,Num,Integral,Real,Enum)
+instance Show IcAmount where
+    show (IcAmount i) = 'x':show i