def check_substring(string, sample) :
  import re 
   
  if (sample in string): 
      y = "\A" + sample 
      x = re.search(y, string) 
      if x : 
          return ("string starts with the given substring") 
      else : 
          return ("string doesnt start with the given substring") 
  else : 
      return ("entered string isnt a substring")
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] 