import decimal
import math
N = int(input())

A = [4,3]
B = [1,1]

for i in range(2,N+1):
    a0,b0 = A[i-2],B[i-2]
    a1,b1 = A[i-1],B[i-1]

    x = 19*a1*b0 - 12*a0*b1
    y = b0 * b1 * 4
    g = math.gcd(x,y)
    
    x //= g
    y //= g
    A.append(x)
    B.append(y)

print(decimal.Decimal(A[N]/B[N]))