def sort_on_occurence(lst):
	 
	dct = {} 
	for i, j in lst: 
		dct.setdefault(i, []).append(j) 
	return ([(i, *dict.fromkeys(j), len(j)) 
				for i, j in dct.items()]) 
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] 