diff --git a/src/main/kotlin/lesson1/idiom0.kt b/src/main/kotlin/lesson1/idiom0.kt
new file mode 100644
index 0000000..b7da0ad
--- /dev/null
+++ b/src/main/kotlin/lesson1/idiom0.kt
@@ -0,0 +1,15 @@
+package lesson1
+
+/**
+ * This is the entry point of the program. The body of this method is considered to be the body of the program.
+ * `suspend` modifier allows to launch the program in asynchronous mode and could be omitted. [args] are used to pass
+ * console arguments in a desktop application and also could be omitted.
+ *
+ * On JVM there could be several entry points that a distinguished by their fully-qualified name with kotlin-to-JVM
+ * transformation (capitalized + Kt suffix).
+ *
+ * In Kts/Jupyter/Worksheet main function is absent. The body of the script plays that role.
+ */
+suspend fun main(args: Array<String>) {
+    println("Hello Kotlin from MIPT!")
+}
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diff --git a/src/main/kotlin/lesson1/idiom1.kt b/src/main/kotlin/lesson1/idiom1.kt
new file mode 100644
index 0000000..3e5034b
--- /dev/null
+++ b/src/main/kotlin/lesson1/idiom1.kt
@@ -0,0 +1,26 @@
+package lesson1
+
+/**
+ * Interpolated string allow to construct string fast
+ */
+fun main() {
+    println("This is a plain string")
+
+    val arg = "Interpolated"
+    println("This is an $arg string")
+
+    val number = 1
+    println("This is an $arg string number ${number + 1}")
+
+    println("This is a string with \$")
+
+    println("""
+        This is a 
+            multi
+                line
+                    raw
+                        string
+    """.trimIndent())
+
+    println("""This is a raw string number ${number+1} with \ and ${'$'} """)
+}
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diff --git a/src/main/kotlin/lesson1/idiom2.kt b/src/main/kotlin/lesson1/idiom2.kt
new file mode 100644
index 0000000..f7053c3
--- /dev/null
+++ b/src/main/kotlin/lesson1/idiom2.kt
@@ -0,0 +1,21 @@
+package lesson1
+
+/**
+ * `val` means read-only property
+ *
+ * `var` means writeable property
+ *
+ * Unnecessary use of `var` is not recommended.
+ *
+ * **NOTE:** In performance critical cases explicit cycles are better, but mutable state should be encapsulated.
+ */
+fun main() {
+    /* Not recommended */
+    var counter = 0
+    for(i in 0..20){
+        counter += i
+    }
+
+    /* recommended */
+    val sum = (0..20).sum()
+}
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diff --git a/src/main/kotlin/lesson1/idiom3-5.kt b/src/main/kotlin/lesson1/idiom3-5.kt
new file mode 100644
index 0000000..3aa42ea
--- /dev/null
+++ b/src/main/kotlin/lesson1/idiom3-5.kt
@@ -0,0 +1,42 @@
+package lesson1
+
+//preamble
+
+/**
+ * Functions could be defined everywhere in kotlin code. This is a so-called top-level function.
+ */
+fun doSomething(){
+    println("I did it")
+}
+
+object AnObject{
+    /**
+     * This is a member-function
+     */
+    fun doSomethingInAnObject(){
+        println("I did it in an object")
+    }
+}
+
+fun doSomethingSpecial(){
+    /**
+     * This one is inside another function
+     */
+    fun doSomethingInside(){
+        println("I did it inside another function")
+    }
+    doSomethingInside()
+}
+
+//idiom 3 - Unit
+fun returnUnit(): Unit{
+    // no return statement `Unit` is returned implicitly
+}
+
+//idiom 4 - default parameters
+fun doSomethingWithDefault(a: Int = 0, b: String = ""): String {
+    return "A string with a == $a and b == $b"
+}
+
+//idiom 5 - function body shortcut
+fun theSameAsBefore(a: Int = 0, b: String = ""): String = "A string with a == $a and b == $b"
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diff --git a/src/main/kotlin/main.kt b/src/main/kotlin/main.kt
deleted file mode 100644
index 5322214..0000000
--- a/src/main/kotlin/main.kt
+++ /dev/null
@@ -1,5 +0,0 @@
-package ru.mipt.npm.ks.demo
-
-fun main() {
-    println("Hello Kotlin from MIPT!")
-}
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