Interesting polygon

Vasya drew a convex polygon with sides of length 1, 2, 3, ..., n (4 ≤ n ≤ 30), and then built the circle around it. Find the radius r of the circle drawn around the polygon by Vasya.

Input

Number of sides n in a polygon.

Output

Print radius r of a circle with 8 digits after the decimal point.

Examples