diff --git a/persian_tools/separator.py b/persian_tools/separator.py
index 48ca0cc..e0a013c 100644
--- a/persian_tools/separator.py
+++ b/persian_tools/separator.py
@@ -1,16 +1,16 @@
-from typing import Union
+from typing import TypeAlias
 import re
 
+Number: TypeAlias = int | float | str
 
-def add(number: Union[int, float, str], separator: str = ',') -> str:
-    number = str(number)
-    parts = number.split('.')
-    pattern = '(\\d)(?=(\\d{3})+(?!\\d))'
-    repl = r'\1{sep}'.format(sep=separator)
+_PATTERN = re.compile(r"(\d)(?=(\d{3})+(?!\d))")
 
-    parts[0] = re.sub(pattern, repl, parts[0])
-    return '.'.join(parts)
 
+def add(number: Number, separator: str = ",") -> str:
+    integer, *decimal = str(number).split(".")
+    integer = _PATTERN.sub(rf"\1{separator}", integer)
+    return ".".join((integer, *decimal))
 
-def remove(number: str, separator: str = ',') -> str:
-    return str(number).replace(separator, '')
+
+def remove(number: str, separator: str = ",") -> str:
+    return number.replace(separator, "")