class Calculator 
{
	String   xInput ="0";
	
	char     operator = ' ';
	boolean  newCalc = true;
	public int yAkku;
	protected transient java.beans.PropertyChangeSupport propertyChange = new java.beans.PropertyChangeSupport(this);
	String fieldXInput = "";
public  String appendInput (String label)
{
	if ( newCalc )
	{
		xInput = label;
		newCalc = false;
  }
  else
  {
  	   xInput = xInput + label;
  }
  
  return xInput;	 
}
public String clear () 
{
	xInput = "0";
	yAkku  = 0;
	operator = ' ';
	newCalc = true;
	
	return xInput;
}
public String function (String op) 
{
	 int xReg = 0;
	 
	 try
	 {
	 	  xReg = Integer.parseInt (xInput);
	 }
	 catch (Exception e) {};
	 
	 switch (operator)
	 {
	 	case  '+':
	 	   yAkku = yAkku + xReg;
	 	   break;
	 	case  '-':
	 	   yAkku = yAkku - xReg;
	 	   break;   
	 	case  '*':
	 	   yAkku = yAkku * xReg;
	 	   break;  
	 	case  '/':
	 	   yAkku = yAkku / xReg;
	 	   break;   
	 	default:   
	 	   yAkku = Integer.parseInt (xInput);
	 }
	 
	 xInput = Integer.toString (yAkku);
	 operator = op.charAt (0);
   newCalc = true;
	 
	 if ( op == "=" )
	 {
	 	 yAkku = 0;
	 } 	 
  
   return xInput;
}
}