def find_largest_digit_helper(n, lar):
	"""
	This is the help function to find the largest digit
	:param n  :(int) the number to find the largest digit
	:param lar:(int) found the largest digit
	:return   :(int) the largest digit
	"""
	if n < lar:
		return lar
	else:
		if n % 10 > lar:
			lar = n % 10

		return find_largest_digit_helper(int(n/10), lar)