diff --git a/merge-csv-lists.py b/merge-csv-lists.py
index 71473ae..8dc5b56 100644
--- a/merge-csv-lists.py
+++ b/merge-csv-lists.py
@@ -2,37 +2,31 @@
 import argparse
 
 
-def split_and_flat(input_string):
-    if "\n" in input_string:
-        _without_newlines = input_string.split("\n")
-        _without_empty = filter(lambda x: x != "", _without_newlines)
-        input_string = ",".join(_without_empty)
-    comma_split = input_string.split(",")
-    flat_list = []
-    for item in comma_split:
-        dash_split = item.split("-")
-        flat_list.extend([value.strip().replace("\n", "") for value in dash_split])
+def flatten_and_split(input_string):
+    elements = input_string.replace("\n", "").split(",")
+    flat_list = [item.strip() for element in elements for item in element.split("-")]
     return ",".join(flat_list)
 
 
-def unique_combined_list(*inputs):
+def combine_and_uniquify(*inputs):
     combined_list = [
         item.strip().title() for input_list in inputs for item in input_list.split(",")
     ]
-    final_list = []
-    for name in combined_list:
+    unique_names = set(combined_list)
+
+    final_set = set()
+    for name in unique_names:
         parts = name.split()
         if len(parts) == 2:
             first, last = parts
             reversed_name = f"{last} {first}"
-            if name not in final_list and reversed_name not in final_list:
-                final_list.append(name)
+            # Add the name if its reversed variant is not already in the final set
+            if reversed_name not in final_set:
+                final_set.add(name)
         else:
-            if name not in final_list:
-                final_list.append(name)
-    sorted_list = sorted(final_list)
-    output = ",".join(sorted_list)
-    return output
+            final_set.add(name)
+
+    return ",".join(sorted(final_set))
 
 
 def main():
@@ -41,13 +35,9 @@ def main():
     )
     parser.add_argument("lists", nargs="+", type=str, help="Comma-separated lists.")
     args = parser.parse_args()
-    if len(args.lists) == 1:
-        args.lists.append(args.lists[0])
 
-    # Process each list with split_and_flat if it contains a dash
-    processed_lists = [split_and_flat(lst) if "-" in lst else lst for lst in args.lists]
-
-    result = unique_combined_list(*processed_lists)
+    processed_lists = [flatten_and_split(lst) for lst in args.lists]
+    result = combine_and_uniquify(*processed_lists)
     print(result)