zad3_2

#!/usr/bin/python3
import sys
import re

n = input('PODAJ N: ')
n = int(n)
t = input('PODAJ T: ')
podzial = t.split()
pom = []
tablica = [0]*n

for i in podzial:
    pom.append(int(i))

for i in range(n):
    if i in pom:
        tablica[i-1] = 1 - tablica[i-1]

pot = n-1
elm = rank = 0
for i in tablica:
    if i == elm:
        elm = 0
    else:
        rank += 2**pot
        elm = 1
    pot -= 1
print(rank)