def equilibrium_index(arr):
  
  total_sum = sum(arr)
  left_sum=0
  for i, num in enumerate(arr):
    total_sum -= num
    if left_sum == total_sum:
      return i
    left_sum += num
  return -1
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] 