Piecewise Function

Problem Description

Write a program to compute the value of the following piecewise function $y=f(x)$.

$$\begin{cases} y=-x+2.5,\quad &0 \le x \lt 5\\ y=2-1.5(x-3)(x-3),\quad &5 \le x \lt 10\\ y={x\over 2}-1.5,\quad &10 \le x \lt 20 \end{cases}$$

Input Format

A floating-point number $x$, $0 \le x \lt 20$.

Output Format

Output the value of the piecewise function at $x$: $f(x)$, kept to three decimal places.

Sample Input

1.0

Sample Output

1.500

Hint

• Each of the three intervals uses its own formula; get the endpoint assignment right: which segment does $x=5$ fall into? Which does $x=10$ fall into?
• Keep $3$ decimal places.
• Verify with the sample: 1.0 → 1.500.