public void doSomeWork(Prac4 prog)
 {
     prog.getFirstNumber();
     prog.getSecondNumber();
     prog.getOperator();
     prog.performCalculation();
     prog.displayResult();
     doSomeWork(prog);
 }
 public static void Main4(string[] args)
 {
     Prac4 prog = new Prac4();
     prog.doSomeWork(prog);
 }