def nCr(n, r):
    result = 1
    for i in range(1, r + 1):
        result = result * (n - i + 1) // i
    return result

def sugoroku(N):
    limit = N // 2 + N % 2
    num = N
    cnt = 0
    while num >= limit:
        cnt += nCr(num, N - num)
        num = num - 1
    return cnt

if __name__ == '__main__':
    N = int(input())
    print(sugoroku(N))