Problems
The square and triangle
The square and triangle
Given a square with side a, in which an isosceles triangle is inscribed. Determine the area of this triangle.
Input
One real number a (1 ≤ a ≤ 1018).
Output
Print one number - the area of the triangle.
Input example #1
2
Output example #1
2
Input example #2
4.4
Output example #2
9.68