import java.io.*;
class Test{
public static void main(String agc[]){
tyte[] buf=new tyte[50];
String temp=null;
double banjing=0;
try{
System.out.println("输入半径:");
System.in.read(buf);
temp=new String(buf);
banjing=Double.paresDouble(temp);
}catch(Exception e){}
System.out.println("面积:"+Math.PI*banjing*banjing);
}
}