import sys

sys.setrecursionlimit(10 ** 6)
import fractions
# from itertools import *
from bisect import *
# from math import *
from collections import *
from heapq import *
from random import *
from decimal import *
import numpy as np

int1 = lambda x: int(x) - 1
p2D = lambda x: print(*x, sep="\n")
def II(): return int(sys.stdin.readline())
def MI(): return map(int, sys.stdin.readline().split())
def MI1(): return map(int1, sys.stdin.readline().split())
def MF(): return map(float, sys.stdin.readline().split())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LI1(): return list(map(int1, sys.stdin.readline().split()))
def LF(): return list(map(float, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
dij = [(0, 1), (1, 0), (0, -1), (-1, 0)]

def main():
    n = II()
    aa = [[fractions.Fraction(1, 1), fractions.Fraction(0, 1)], [fractions.Fraction(0, 1), fractions.Fraction(1, 1)]]
    for _ in range(n - 1):
        a10, a11 = aa[-1]
        a20, a21 = aa[-2]
        aa.append([(19 * a10 - 12 * a20) / 4, (19 * a11 - 12 * a21) / 4])
    d4 = Decimal(4)
    d3 = Decimal(3)
    f0, f1 = aa[n]
    num0, den0 = f0.as_integer_ratio()
    num1, den1 = f1.as_integer_ratio()
    ans = d4 * num0 / den0 + d3 * num1 / den1
    print(ans)

main()