print('Hello, World!')

for i in range(1, 5):
	print(i)

arr = [1, 2, 3, 4, 5]
arr.reverse()
print(arr)

import threading

def print_numbers():
	for i in range(1, 11):
		print(i)

def print_letters():
	for letter in 'abcdefghij':
		print(letter)

thread1 = threading.Thread(target=print_numbers)
thread2 = threading.Thread(target=print_letters)

thread1.start()
thread2.start()

class Person:
	def __init__(self, name, age):
		self.name = name
		self.age = age

p1 = Person('John', 36)
print(p1.name)
print(p1.age)

def factorial(n):
	if n == 0:
		return 1
	else:
		return n * factorial(n-1)

print(factorial(5))