Problem Description

The lengths of the three sides of a triangle are $a$, $b$, and $c$. Its area is $\sqrt{p(p-a)(p-b)(p-c)}$, where $p=\frac{1}{2}(a+b+c)$. Given these three numbers, compute the area of the triangle and round it to $1$ decimal place.

Input Format

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

Output Format

Output one real number representing the area of the triangle, accurate to $1$ digit after the decimal point.

3 4 5

6.0

Hint

Constraints: The testdata guarantees that a triangle can be formed. $0\leq a,b,c\leq 1000$. Each side length has at most $2$ digits after the decimal point in the input.

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