import java.io.*; import java.util.*; class Main89 { public static void main (String[] args) throws IOException { BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); double c = Double.parseDouble(br.readLine()); String[] line = br.readLine().split(" "); double in = Double.parseDouble(line[0]); double out = Double.parseDouble(line[1]); System.out.println(1.0 / 4.0 * Math.pow(Math.PI, 2) * (in + out) * Math.pow(out - in, 2) * c); } }