def sub_lists(my_list):
	from itertools import combinations
	
	subs = []
	for i in range(0, len(my_list)+1):
	  temp = [list(x) for x in combinations(my_list, i)]
	  if len(temp)>0:
	    subs.extend(temp)
	return subs
def count_ways(n):
	 
	A = [0] * (n + 1) 
	B = [0] * (n + 1) 
	A[0] = 1
	A[1] = 0
	B[0] = 0
	B[1] = 1
	for i in range(2, n+1): 
		A[i] = A[i - 2] + 2 * B[i - 1] 
		B[i] = A[i - 1] + B[i - 2] 
	return A[n] 