diff --git a/.gitignore b/.gitignore
index 5564fa0a305..7b110e04948 100644
--- a/.gitignore
+++ b/.gitignore
@@ -48,3 +48,5 @@ dist
 generated
 .next
 .teamcity/*.iml
+.idea/misc.xml
+.idea/vcs.xml
diff --git a/.idea/misc.xml b/.idea/misc.xml
deleted file mode 100644
index 3fa0c744367..00000000000
--- a/.idea/misc.xml
+++ /dev/null
@@ -1,7 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<project version="4">
-  <component name="JavaScriptSettings">
-    <option name="languageLevel" value="ES6" />
-  </component>
-  <component name="ProjectRootManager" version="2" project-jdk-name="Python 3.6 (kotlin-web-site)" project-jdk-type="Python SDK" />
-</project>
\ No newline at end of file
diff --git a/.idea/vcs.xml b/.idea/vcs.xml
deleted file mode 100644
index bafeaf22976..00000000000
--- a/.idea/vcs.xml
+++ /dev/null
@@ -1,12 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<project version="4">
-  <component name="GitSharedSettings">
-    <option name="FORCE_PUSH_PROHIBITED_PATTERNS">
-      <list />
-    </option>
-  </component>
-  <component name="VcsDirectoryMappings">
-    <mapping directory="$PROJECT_DIR$" vcs="Git" />
-    <mapping directory="$PROJECT_DIR$/kotlinx.coroutines" vcs="Git" />
-  </component>
-</project>
\ No newline at end of file
diff --git a/docs/topics/set-operations.md b/docs/topics/set-operations.md
index ba66f40e9f9..4c745b33d0c 100644
--- a/docs/topics/set-operations.md
+++ b/docs/topics/set-operations.md
@@ -5,12 +5,8 @@ or subtracting collections from each other.
 
 To merge two collections into one, use the [`union()`](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.collections/union.html)
 function. It can be used in the infix form `a union b`.
-Note that for ordered collections the order of the operands is important: in the resulting collection, the elements of the
-first operand go before the elements of the second.
-
-To find an intersection between two collections (elements present in both of them), use [`intersect()`](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.collections/intersect.html).
-To find collection elements not present in another collection, use [`subtract()`](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.collections/subtract.html). 
-Both these functions can be called in the infix form as well, for example, `a intersect b`.
+Note that for ordered collections the order of the operands is important. In the resulting collection, the elements of the
+first operand go before the elements of the second:
 
 ```kotlin
 fun main() {
@@ -19,7 +15,20 @@ fun main() {
 
     println(numbers union setOf("four", "five"))
     println(setOf("four", "five") union numbers)
+    // output according to the order
+//sampleEnd
+}
+```
+{kotlin-runnable="true" kotlin-min-compiler-version="1.3"}
 
+To find an intersection between two collections (elements present in both of them), use [`intersect()`](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.collections/intersect.html).
+To find collection elements not present in another collection, use [`subtract()`](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.collections/subtract.html). 
+Both these functions can be called in the infix form as well, for example, `a intersect b`:
+
+```kotlin
+fun main() {
+//sampleStart
+    val numbers = setOf("one", "two", "three")
     println(numbers intersect setOf("two", "one"))
     println(numbers subtract setOf("three", "four"))
     println(numbers subtract setOf("four", "three"))
@@ -47,7 +56,7 @@ fun main() {
 
 You can also apply `union()`, `intersect()`, and `subtract()` to `List`.
 However, their result is _always_ a `Set`, even on lists. In this result, all the duplicate elements are merged into one 
-and the index access is not available.
+and the index access is not available:
 
 ```kotlin
 fun main() {