import sys

def fact(n):
    f=1
    for i in range(1,n+1,1):
        f=f*i
    return f


n = int(raw_input().strip())
m = map(int, raw_input().strip().split(' '))
t=2


for i in range(2,n,1):
    for j in range(1,i+1,1):
        t=t+fact(i)/(fact(i)*fact(i-j))
    
    
print t