public static string timeConversion(string s)
{
    bool isPM = s.Substring(8, 2) == "PM";
    string hourFormat = s.Substring(0, 8);
    int hour = int.Parse(hourFormat.Substring(0, 2));
    hourFormat = hourFormat.Remove(0, 2);

    if (!isPM)
    {
        if(hour == 12)
        return "00" + hourFormat;

        return hour < 9 ? "0" + hour + hourFormat : hour + hourFormat;
    }

    hour = hour == 12 ? hour : hour + 12;
    

    return hour + hourFormat;
}