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.


-----Input-----

The only line of input contains one integer n (1 ≤ n ≤ 55) — the maximum length of a number that a door-plate can hold.


-----Output-----

Output one integer — the maximum number of offices, than can have unique lucky numbers not longer than n digits.


-----Examples-----
Input
2

Output
6

Difficulty: interview

Starter code:

Solutions:
n = int(input())
print(2**(n+1) - 2)


print(2**(int(input())+1)-2)

n = int(input())
res = 0
for i in range(1, n + 1):
    res += 2 ** i
print(res)

n=int(input())
print((2**(n+1))-2)


n = int(input())
print(2 * (2**n - 1))


import sys

n = int(input())
ans = 0

for i in range(1, n + 1):
    ans += (2 ** i)

print(ans)


print(pow(2, int(input()) + 1) - 2)


n = int(input())
print(sum([2**i for i in range(1, n+1)]))

n = int(input())
print(2 ** (n+1) - 2)


print(2**(int(input())+1)-2)

n = int(input())
ans = 0
for i in range(1, n + 1):
    ans += 2 ** i
print(ans)


print(2 ** (int(input()) + 1) - 2)

n = int(input())
sum = int()
for i in range (n):
    sum = sum + 2**(i + 1)
print(sum)


n = int(input())
s = [2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768, 65536, 131072, 262144, 524288, 1048576, 2097152, 4194304, 8388608, 16777216, 33554432, 67108864, 134217728, 268435456, 536870912, 1073741824, 2147483648, 4294967296, 8589934592, 17179869184, 34359738368, 68719476736, 137438953472, 274877906944, 549755813888, 1099511627776, 2199023255552, 4398046511104, 8796093022208, 17592186044416, 35184372088832, 70368744177664, 140737488355328, 281474976710656, 562949953421312, 1125899906842624, 2251799813685248, 4503599627370496, 9007199254740992, 18014398509481984, 36028797018963968]
ans = sum(s[:n])
print(ans)

ans = 0
n = int(input())
print(2 ** (n + 1) - 2)

n=int(input())
ret=0
for a in range(1,n+1):
    ret+=2**a
print(ret)


3

n = int(input())

ans = 2**(n+1)-2
print(str(ans))


n = int(input())
ans = 0
mult = 1
for i in range(1, n+1):
    mult *= 2
    ans += mult
print(ans)


n=int(input())
s=0
while(n>=1):
    s+=2**n
    n-=1
print(s)

import re, sys, string, operator, functools, fractions, collections
sys.setrecursionlimit(10**7)
dX= [-1, 1, 0, 0,-1, 1,-1, 1]
dY= [ 0, 0,-1, 1, 1,-1,-1, 1]
RI=lambda x=' ': list(map(int,input().split(x)))
RS=lambda x=' ': input().rstrip().split(x)
mod=int(1e9+7)
eps=1e-6
#################################################
n=RI()[0]
print(pow(2,n+1)-2)







n = int(input())
print(2**(n+1)-2)


n = int(input())

print((2**(n+1)) - 2)


print(2 ** (int(input()) + 1) - 2)

n = int(input())
m = 1
ans = 0
for i in range(1, n + 1):
    m *= 2
    ans += m
print(ans)

n = int(input())
print(2**(n+1)-2)