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

def kaidan(N):
    n1 = N
    n2 = 0
    pat = [[n1, 0]]
    while n1 > 1:
        n1 -= 2
        n2 += 1
        pat.append([n1, n2])
    cnt = 0
    for i in range(len(pat)):
        n = pat[i][0] + pat[i][1]
        r = pat[i][0]
        cnt += nCr(n, r)
    return cnt

def main():
    N = int(input())
    print(kaidan(N))

if __name__ == '__main__':
    main()