Pocky

Pocky is a popular chocolate bar. And also to make an unlucky butler to get one hardly ... But we can get a lot to eat easily.

Apart from the taste, the boring student L likes to take out one by one to make a regular polygon.

And after that, he would like to know the area of the regular polygon.

Input

One line for each case, only one positive integer N (N ≤ 32768). Indicate the number of the regular polygon's edges. And the length of every regular polygon's edge is 1 permanently.

The case N < 3, indicate the end of input, and no output for it.

Output

A real number for each case, indicate the area of the regular polygon. Retained two digits after the decimal point.

Examples