public static String timeConversion(String s) {
// Write your code here
    String hours = s.substring(0,2) ;
    String restOfTime = s.substring(2,8);
    String meridian = s.substring(8);

    if((meridian.equals("PM")) && !hours.equals("12")){
        hours = String.valueOf(Integer.parseInt(hours)+12) ;
        }else if(meridian.equals("AM") && hours.equals("12")){
            hours="00";
        }

    return hours + restOfTime;
}