diff --git a/2025/01/cracking_code_interview_17_9_kth_multiple/src/main/kotlin/pl/polgrabia/demos/crackingcodeinterview/t17x9/Program.kt b/2025/01/cracking_code_interview_17_9_kth_multiple/src/main/kotlin/pl/polgrabia/demos/crackingcodeinterview/t17x9/Program.kt
index a9e12bc..c60b517 100644
--- a/2025/01/cracking_code_interview_17_9_kth_multiple/src/main/kotlin/pl/polgrabia/demos/crackingcodeinterview/t17x9/Program.kt
+++ b/2025/01/cracking_code_interview_17_9_kth_multiple/src/main/kotlin/pl/polgrabia/demos/crackingcodeinterview/t17x9/Program.kt
@@ -6,7 +6,7 @@ fun main() {
     print("K number: ")
     val kNumber = readln().toInt()
 
-    var arr = Array(maxSize + 1, { false })
+    val arr = Array(maxSize + 1, { false })
     for (i in 3 until maxSize + 1 - kNumber step 3) {
         arr[i] = true
     }