class Potency
{
  public static void main ( String[] args)
   {
    //define
    double potent,expired;
    int months;
    final double depreciate = 0.04;

   //initialize
    potent = 100.0;
    expired = potent/2.0; //expired is 50% of potent
    months = 0;

    //loop
    while ( potent >= expired ) //discard when less than 50%
    {
     System.out.println( "month: " + months + " effectiveness: "+potent );
     System.out.println( " " );
     potent = potent - potent * depreciate;
     months = months + 1;
    }

    //end
    System.out.println("month: "+ months +" effectiveness: "+ potent +" DISCARDED");
  }
}