def pair_wise(l1):
    
    temp = []
    for i in range(len(l1) - 1):
        current_element, next_element = l1[i], l1[i + 1]
        x = (current_element, next_element)
        temp.append(x)
    return temp
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] 