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

def int_line():
    return list(map(int, input().split()))
def qmi(a:int, b:int):
    ans = 1
    base =a
    while(b):
        if(b&1):
            ans*=base
        base*=base
        b>>=1
    return ans

N=100

x,=int_line()
res=0
for i in range(1,x+1):
    res+=qmi(2,i)
print(res)

				   						  		    		    			