diff --git a/README.md b/README.md
index 4a1b700..83bf90d 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,11 @@
 # Opencv Tutorial
 
+## Install
+
+`pip install opencv-python`
+
+## Articles
+
 I highly recommend to see my articles for better understanding:
 
 Part_1: https://habr.com/ru/post/519454/
diff --git a/part_4.py b/part_4.py
index 7116bbb..011f025 100644
--- a/part_4.py
+++ b/part_4.py
@@ -25,7 +25,7 @@ def find_features(img1):
 def find_contours_of_cards(image):
     blurred = cv2.GaussianBlur(image, (3, 3), 0)
     T, thresh_img = cv2.threshold(blurred, 215, 255, cv2.THRESH_BINARY)
-    (_, cnts, _) = cv2.findContours(thresh_img, cv2.RETR_EXTERNAL,
+    (cnts, _) = cv2.findContours(thresh_img, cv2.RETR_EXTERNAL,
                                     cv2.CHAIN_APPROX_SIMPLE)
     return cnts
 
@@ -54,4 +54,4 @@ def draw_rectangle_aroud_cards(cards_coordinates, image):
     gray_main_image = cv2.cvtColor(main_image, cv2.COLOR_BGR2GRAY)
     contours = find_contours_of_cards(gray_main_image)
     cards_location = find_coordinates_of_cards(contours, gray_main_image)
-    draw_rectangle_aroud_cards(cards_location, main_image)
\ No newline at end of file
+    draw_rectangle_aroud_cards(cards_location, main_image)
diff --git a/requirements.txt b/requirements.txt
new file mode 100644
index 0000000..0e118d4
--- /dev/null
+++ b/requirements.txt
@@ -0,0 +1 @@
+opencv-python>=4.0
\ No newline at end of file