N = int(input())
T = [1] + [0]*4
for n in range(N-1):
    for k in [4, 3, 2, 1]:
        T[k] = T[k]*((k+1)/6) + T[k-1]*((6-k)/6)
    T[0] = T[0]*(1/6)
print(1-sum(T))