n=int(input())
q=1
z=2
h=0
for i in range(3,n+1):
  h=q+z*2
  q=z
  z=h
if n==1:
  print(1)
elif n==2:
  print(2)
else:
  print(z)
/**************************************************************
	Problem: 1369
	User: admin
	Language: Python
	Result: Accepted
	Time:137 ms
	Memory:34480 kb
****************************************************************/