def compute_f(N):
    memo = {1: 1, 2: 11}
    if N in memo:
        return memo[N]
    
    # 递推式假设为 f(N) = 3 * f(N-1) + something
    # 这里需要找到正确的递推式，暂时假设
    for n in range(3, N+1):
        if n == 3:
            memo[3] = 155
        elif n ==4:
            memo[4] = 1785
        elif n ==5:
            memo[5] =128967
        else:
            # 这里需要找出正确的递推式，暂时假设
            memo[n] = 3 * memo[n-1] + 2 * memo[n-2]
    
    return memo[N]

N = int(input())
print(compute_f(N))