Concise mathematics problem

Time Limit: 2 Seconds
Memory Limit: 65536 KB

F_{0}(x) = sin(x) / x

F_{1}(x)= (sin(x) - x * cos(x)) / x / x

F_{n+1}(x) = (2 * n + 1) * F_{n}(x) / x - F_{n-1}(x)

You are to calculate F_{n}(x) for given n and x.

**Input**

There are multiple test cases. Each test case consists of one line containing two numbers. The first number specifies *n*, a non-negative integer not more than 20. The second number specifies *x*, a positive real number between 0.10 and 20.00.

**Output**

For each test case, output F_{n}(x), using scientific expression with four valid digits as the sample output. It is guaranteed that the exponentials of the answers are all negative.

**Sample Input**

3 10.0
5 1.00
8 0.10

**Sample Output**

-3.950*10^-2
9.256*10^-5
2.901*10^-16

**Author: ***HE, Rongqiang*

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