diff --git a/5-0-functional-programming/5-0-2-stream-sum-of-squares/src/main/java/com/bobocode/fp/SumOfSquares.java b/5-0-functional-programming/5-0-2-stream-sum-of-squares/src/main/java/com/bobocode/fp/SumOfSquares.java
index a3d7f2d92..06f8e214b 100644
--- a/5-0-functional-programming/5-0-2-stream-sum-of-squares/src/main/java/com/bobocode/fp/SumOfSquares.java
+++ b/5-0-functional-programming/5-0-2-stream-sum-of-squares/src/main/java/com/bobocode/fp/SumOfSquares.java
@@ -27,11 +27,8 @@ static int calculateSumOfSquaresInRange(int startInclusive, int endInclusive) {
             throw new InvalidRangeException();
         }
 
-        // todo: refactor using functional approach – instead of using for loop, use IntStream.rangeClose()
-        int sumOfSquares = 0;
-        for (int i = startInclusive; i <= endInclusive; i++) {
-            sumOfSquares += i * i;
-        }
-        return sumOfSquares;
+        return IntStream.rangeClosed(startInclusive, endInclusive)
+                .map(a -> a * a)
+                .sum();
     }
 }