diff --git a/lab4/app/Main.hs b/lab4/app/Main.hs
index 4c6b30f..33000ba 100644
--- a/lab4/app/Main.hs
+++ b/lab4/app/Main.hs
@@ -3,4 +3,7 @@ module Main (main) where
 import Lib
 
 main :: IO ()
-main = someFunc
+main = do
+  putStrLn $ "Примеры работы `isCongruent`"
+  putStrLn $ "isCongruent 10 12 2: " ++ show (isCongruent 10 12 2)
+  putStrLn $ "isCongruent 10 11 2: " ++ show (isCongruent 10 11 2)
\ No newline at end of file
diff --git a/lab4/src/Lib.hs b/lab4/src/Lib.hs
index d36ff27..382853f 100644
--- a/lab4/src/Lib.hs
+++ b/lab4/src/Lib.hs
@@ -1,6 +1,6 @@
 module Lib
-    ( someFunc
+    ( isCongruent
     ) where
 
-someFunc :: IO ()
-someFunc = putStrLn "someFunc"
+isCongruent :: Int -> Int -> Int -> Bool
+isCongruent a b d = a `mod` d == b `mod` d