**Time limit:**1.00 s**Memory limit:**512 MB

**Input**

The only input line contains three integers $n$, $a$ and $b$.

**Output**

Print the probability rounded to six decimal places.

**Constraints**

- $1 \le n \le 100$

- $1 \le a \le b \le 6n$

**Example**

Input:

`2 9 10`

Output:

`0.194444`