func main()
	var a: float :: cui@inputFloat()
	var b: float :: cui@inputFloat()
	var c: float :: cui@inputFloat()
	var s: float :: (a + b + c) / 2.0
	
	var ans: float :: lib@sqrt(s * (s - a) * (s - b) * (s - c)) / 4.0
	do cui@print("\{ans}\n")
end func