def sol(n):
    if n == 0 or n == 1:
        return 1
    dp = [0] * (n+1)
    dp[:2] = [1, 1]
    for i in range(2, n+1):
        dp[i] = dp[i-1] + 2 * dp[i-2]
    return dp[n]
while True:
    try:
        n = int(input())
        print(sol(n))
    except:
        break