Sum of sines#11442
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Sum of sines

1 second
128 megabytes
Very easy

For the given positive integer and real number find the sum

\sin~x + \sin^2 x + \dots + \sin^n x

Input

Two numbers: one integer n~(n \le 1000) and one real number x~(|x| \le 1000).

Output

Print the value of the sum with decimal digits.

Examples

Example 1

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