diff --git a/main.kt b/main.kt
index 11ce4a3..0787d7b 100644
--- a/main.kt
+++ b/main.kt
@@ -1,5 +1,40 @@
 package my.program
 
+
+// L4: Function.
+
+fun memory_generateConstPlayfield(
+  n: Int
+): Map<Int, Int> {
+  var idGroups: MutableMap<Int, Int> = mutableMapOf()
+  var id = 0
+  for (gid in 0..<n) {
+    idGroups[id] = gid
+    id += 1
+    idGroups[id] = gid
+    id += 1
+  }
+  return idGroups
+}
+
+// L20: Test.
+
+fun test_memory_generateConstPlayfield(): String {
+  val idGroups = memory_generateConstPlayfield(2)
+  if (
+    idGroups.count() == 4 &&
+    idGroups[0] == 0 &&
+    idGroups[1] == 0 &&
+    idGroups[2] == 1 &&
+    idGroups[3] == 1
+  ) {
+    return "OK: memory_generateConstPlayfield"
+  }
+  return "ERR: memory_generateConstPlayfield"
+}
+
+// L36: Run.
+
 fun main(args: Array<String>) {
-  println("Hello, World from Kotlin")
+  println(test_memory_generateConstPlayfield())
 }