public class Ex4 {

 public static void main(String[] args) {
 if(args.length < 1 | args.length > 3){System.out.println("number of
 arguments invalid");}

 else{
 try{
 double a = Double.parseDouble(args[0]);
 double b = Double.parseDouble(args[1]);
 double c = Double.parseDouble(args[2]);

 if(args.length ==1){System.out.println(a);}

 else if (args.length == 2){System.out.println(a*b);}

    else if(args.length == 3){System.out.println(a*b*c);}

}
catch(NumberFormatException e){System.out.println("invalid operation");}
}
}
}
}