def unique_in_order(s):
	if len(s) < 1:
		return []
	prev_sym = s[0]
	result = [prev_sym]
	for sym in s[1:]:
		if sym == prev_sym:
			continue
		result.append(sym)
		prev_sym = sym
	return result

print(unique_in_order('AAAABBBCCDAABBB'))