def twoDimArray(row,column,n): return [[n for j in range(column)] for i in range(row)]
n=int(input())
dp=twoDimArray(n,7,0)
dp[0][1]=1.0
for i in range(1,n):
    for j in range(1,7):
        dp[i][j]=j/6*dp[i-1][j]+(1-(j-1)/6)*dp[i-1][j-1]
print(dp[n-1][6])