diff --git a/common_module.py b/common_module.py
index e0f8966..7c4c454 100644
--- a/common_module.py
+++ b/common_module.py
@@ -12,8 +12,8 @@ class CommonModule:
 
     @classmethod
     def index_by_f2c (cls, string: str, index: float) -> int:
-        i = 0
-        work = ''
+        i: int = 0
+        work: str = ''
         for c in string:
             work += c
             if cls.len_by_full (work) > index:
@@ -25,7 +25,7 @@ class CommonModule:
 
     @classmethod
     def mid_by_full (cls, string: str, start: float, length: float) -> str:
-        trimmed_left = string[cls.index_by_f2c (string, start):]
+        trimmed_left: str = string[cls.index_by_f2c (string, start):]
 
         return trimmed_left[:cls.index_by_f2c (trimmed_left, length)]