Triangle Area

Problem Source

Luogu P5708

Problem Description

A triangle has side lengths $a$, $b$, $c$; its area is $\sqrt{p(p-a)(p-b)(p-c)}$, where $p = \frac{1}{2}(a+b+c)$. Input these three numbers and compute the area of the triangle, rounded to $1$ decimal place.

Input Format

The first line contains three real numbers $a, b, c$, separated by spaces.

Output Format

Output one real number: the area of the triangle, kept to $1$ decimal place.

Sample Input

3 4 5

Sample Output

6.0

Hint

• Heron's formula was used in the previous problem: compute $p$ first, then apply the formula. The new thing here is the output: keep 1 decimal place.
• The sides are decimals, so choose the right type.
• Check against the sample: 3 4 5 → 6.0.

The data guarantees a valid triangle can be formed, with $0 \le a, b, c \le 1000$, and each side having at most $2$ decimal places on input.