Add Lesson 2 Task 3

Lesson_2/task3.py

@@ -0,0 +1,27 @@
+# Lesson 2 Task 3: display all numbers from n to 1, then remove the first number and repeat while n > 0
+# Author: Stanislav Mykhailenko
+# License: Unlicense
+
+# Return codes:
+# 0 - OK
+# 1 - Invalid number entered
+
+import math, sys
+
+def numberError():
+	print("Invalid number entered.")
+	sys.exit(1)
+
+try: number = int(input("Enter a natural number: "))
+except ValueError: numberError()
+
+if number < 1: numberError()
+
+while number > 0:
+	currentNumber = number
+	while currentNumber > 0:
+		print(currentNumber, end='')
+		if currentNumber > 1: print(' ', end='')
+		currentNumber = currentNumber - 1
+	print('')
+	number = number - 1