K = int(input())
if K == 1:
    print(1)
    exit()

dp = [-1] * (K+1)
dp[0] = 0
dp[1] = 1
for i in range(2,K+1):
    tmp = 0
    for j in range(1,7):
        tmp += (dp[max(0,i-j)]+1)/6
    dp[i] = tmp

print(dp[-1])