k=int(input())
dp=[0.0]*(k+10)
dp[0]=1.0;dp[1]=-1.0
dp2=[0]*(k+10)
for i in range(k):
    dp[i+1]+=dp[i]
    dp[i+1]+=dp[i]/6
    dp[i+7]-=dp[i]/6
for i in range(k-1,-1,-1):
	dp2[i]+=dp2[i+1]+1.0+(dp2[i+1]-dp2[i+7])/6
print((dp2[0]-dp2[1])/(dp[k]))