import math
from decimal import Decimal, getcontext

getcontext().prec = 200  # Sufficient precision to handle up to N=100

n = int(input())

if n == 0:
    print("4.00000000")
elif n == 1:
    print("3.00000000")
else:
    prepre_num = 4
    prepre_den = 1
    pre_num = 3
    pre_den = 1

    for i in range(2, n + 1):
        new_num = 19 * pre_num * prepre_den - 12 * prepre_num * pre_den
        new_den = 4 * pre_den * prepre_den

        current_gcd = math.gcd(abs(new_num), new_den)
        simplified_num = new_num // current_gcd
        simplified_den = new_den // current_gcd

        prepre_num, prepre_den = pre_num, pre_den
        pre_num, pre_den = simplified_num, simplified_den

    numerator = Decimal(pre_num)
    denominator = Decimal(pre_den)
    result = numerator / denominator

    print("{0:.8f}".format(result))