HW5.25

 public class Solution
 {
     public static void main(String[] args)
     {
         System.out.println(convertMillis(5500));
         System.out.println(convertMillis(100000));
         System.out.println(convertMillis(555550000));
     }

     public static String convertMillis(long millis)
     {
         long totalSeconds = millis / 1000;
         long seconds = totalSeconds % 60;
         long totalMinutes = totalSeconds / 60;
         long minutes = totalMinutes % 60;
         long hours = totalMinutes / 60;
         return hours + ":" + minutes + ":" + seconds;
     }
 }