/*
* Output:
*/
import java.io.BufferedReader;
import java.io.InputStreamReader;
public class MainClass {
public static void main(String args[]) {
try {
InputStreamReader isr = new InputStreamReader(System.in);
BufferedReader br = new BufferedReader(isr);
while (true) {
System.out.print("Radius? ");
String str = br.readLine();
double radius;
try {
radius = Double.valueOf(str).doubleValue();
} catch (NumberFormatException nfe) {
System.out.println("Incorrect format!");
continue;
}
if (radius <= 0) {
System.out.println("Radius must be positive!");
continue;
}
double area = Math.PI * radius * radius;
System.out.println("Area is " + area);
return;
}
} catch (Exception e) {
e.printStackTrace();
}
}
}