The numbers of all offices in the new building of the Tax Office of IT City will have lucky numbers.

Lucky number is a number that consists of digits 7 and 8 only. Find the maximum number of offices in the new building of the Tax Office given that a door-plate can hold a number not longer than *n* digits.
The only line of input contains one integer *n* (1 ≤ *n* ≤ 55) — the maximum length of a number that a door-plate can hold.
none
2
6
1
2
3
14
5
62
12
8190
34
34359738366
43
17592186044414
49
1125899906842622
54
36028797018963966
55
72057594037927934
n = int(input())
print(int((2 ** n -1)*2))
