diff --git a/Lec18/figure/go.mod b/Lec18/figure/go.mod
new file mode 100644
index 0000000..a692304
--- /dev/null
+++ b/Lec18/figure/go.mod
@@ -0,0 +1,3 @@
+module main.go
+
+go 1.24.4
diff --git a/Lec18/figure/main.go b/Lec18/figure/main.go
new file mode 100644
index 0000000..2909470
--- /dev/null
+++ b/Lec18/figure/main.go
@@ -0,0 +1,26 @@
+package main
+
+import (
+	"fmt"
+	"math"
+)
+
+type Cicle struct {
+	radius int
+}
+
+type Rectangle struct {
+	lenght,width int
+}
+
+func (circle Cicle) Perim() float64 {
+	return float64(circle.radius) * math.Pi
+}
+
+
+func main() {
+	c := Cicle{
+		radius: 3,
+	}
+	fmt.Println(c.Perim())
+}
\ No newline at end of file
diff --git a/Lec18/go.mod b/Lec18/go.mod
new file mode 100644
index 0000000..a692304
--- /dev/null
+++ b/Lec18/go.mod
@@ -0,0 +1,3 @@
+module main.go
+
+go 1.24.4
diff --git a/Lec18/main.go b/Lec18/main.go
new file mode 100644
index 0000000..bc38e76
--- /dev/null
+++ b/Lec18/main.go
@@ -0,0 +1,27 @@
+package main
+
+import "fmt"
+
+
+type Employee struct {
+	name string
+	position string
+	salary int
+	currency string
+}
+
+func (e Employee) DisplayInfo() {
+	fmt.Println("Name: ", e.name)
+	fmt.Println("Position: ",e.position)
+	fmt.Printf("Salary: %d %s\n",e.salary,e.currency)
+}
+
+func main(){
+	emp := Employee {
+		name: "Bob",
+		position: "senior",
+		salary: 10000,
+		currency: "RUB",
+	}
+	emp.DisplayInfo()
+}
diff --git a/Lec19/go.mod b/Lec19/go.mod
new file mode 100644
index 0000000..a692304
--- /dev/null
+++ b/Lec19/go.mod
@@ -0,0 +1,3 @@
+module main.go
+
+go 1.24.4
diff --git a/Lec19/main.go b/Lec19/main.go
new file mode 100644
index 0000000..18a0885
--- /dev/null
+++ b/Lec19/main.go
@@ -0,0 +1,37 @@
+package main
+
+import "fmt"
+
+type Student struct {
+	name string
+	age int
+}
+
+type Desriber interface {
+	Describe()
+}
+
+
+func (std Student) Describe(){
+	fmt.Printf("%s and %d y.o",std.name,std.age)
+}
+
+func TypeDescriber(i interface{}){
+	switch v := i.(type){
+		case string:
+			fmt.Println("I am string")
+		case int:
+			fmt.Println("I am int")
+		case Desriber:
+			fmt.Println("I am describer!")
+			v.Describe()
+		default:
+			fmt.Println("Unknown type but I still work!")
+	}
+}
+
+func main() {
+	TypeDescriber(9)
+	std := Student{"Alex", 19}
+	TypeDescriber(std)
+}
diff --git a/Lec20/calculator.go b/Lec20/calculator.go
new file mode 100644
index 0000000..c52e552
--- /dev/null
+++ b/Lec20/calculator.go
@@ -0,0 +1,9 @@
+package main
+
+func add(a,b int) int {
+	return  a + b
+}
+
+func Sub(a,b int) int {
+	return a - b
+}
diff --git a/Lec20/go.mod b/Lec20/go.mod
new file mode 100644
index 0000000..3bdfff5
--- /dev/null
+++ b/Lec20/go.mod
@@ -0,0 +1,3 @@
+module Lec20
+
+go 1.24.4
diff --git a/Lec20/main.go b/Lec20/main.go
new file mode 100644
index 0000000..e44c82a
--- /dev/null
+++ b/Lec20/main.go
@@ -0,0 +1,15 @@
+package main
+
+import (
+	"fmt"
+	"Lec20/rectangle"
+)
+
+func main() {
+	// res := add(2,5)
+	// fmt.Println("Addition equals to ",res)
+
+	r := rectangle.New(10,20,"green")
+	fmt.Println("Perimeter: ",r.Perimeter())
+}
+
diff --git a/Lec20/rectangle/rectangle.go b/Lec20/rectangle/rectangle.go
new file mode 100644
index 0000000..da9e6e8
--- /dev/null
+++ b/Lec20/rectangle/rectangle.go
@@ -0,0 +1,14 @@
+package rectangle
+
+type Rect struct {
+	A,B int
+	color string
+}
+
+func New(newA int, newB int, newColor string) *Rect {
+	return  &Rect{newA,newB,newColor}
+}
+
+func (r *Rect) Perimeter() int {
+	return 2 * (r.A + r.B)
+}
\ No newline at end of file
diff --git a/bin/Lec20 b/bin/Lec20
new file mode 100755
index 0000000..fa4a65d
Binary files /dev/null and b/bin/Lec20 differ