def f(n):
    if n == 0:
        return 0
    elif n == 1:
        return 2
    elif n == 2:
        return 8
    else:
        return 3 * f(n-1) + 2
while True:
    try:
        n = int(input())
        s = f(n)
        print(s)
    except:
        break