// Solution Checker is Broken

import java.util.ArrayList;
import java.util.Arrays;

/**
   Element enumeration defines elements, their symbols, and their melting points.
*/

public enum Element
{
   hydrogen("H", -258.975), oxygen("O", -222.65),
      nitrogen("N", -209.86), chlorine("Cl", -100.84),
         mercury("Hg", -38.72), potassium("K", 63.35),
            sodium("Na", 98.0);

   private String symbol;
   private double meltingPoint;

   Element (String aSymbol, double aMeltingPoint)
   {
      symbol = aSymbol;
      meltingPoint = aMeltingPoint;
   }

   public double getMeltingPoint()
   {
      return meltingPoint;
   }

   public String toString()
   {
      return symbol;
   }

   /**
      Returns a list of elements whose melting points
      are less than or equal to a given temperature.
      @param boundaryTemp the cutoff temperature value
      @return a list of elements that will melt at the boundary temperature
   */
   public static ArrayList<Element> getMeltedElements(double boundaryTemp)
   {
      ArrayList<Element> list = new ArrayList<Element>(Arrays.asList(values()));
      for(int i = 0; i < list.size(); i++)
      {
         if(list.get(i).meltingPoint > boundaryTemp)
         {
            list.remove(i);
            i--;
         }
      }

      return list;
   }
}