public static void main(String[] args) {
        BinarySearchST<String, Integer> st = new BinarySearchST<String, Integer>();
        Out out = new Out("out.txt");
        Out stud = new Out("studA.txt");

        // compute frequency counts
        while (!StdIn.isEmpty()) {
            String key = StdIn.readString();
            if (key.contains(":") || key.startsWith(";")) continue;
            String[] parts = key.split(";");
            String userid = parts[0];

            if (st.contains(userid)) {
                st.put(userid, st.get(userid) + 1);
            }
            else {
                st.put(userid, 1);
            }
        }
        // find user's and their frequency(value)
        for (String user : st.keys()) {
            out.println(user + " " + st.get(user));
        }
        out.println("Student with smallest id :" +st.min());
        out.println("Student with biggest id :" + st.max());

        // find a key with the highest frequency count
        String max = "";
        st.put(max, 0);
        for (String word : st.keys()) {
            if (st.get(word) > st.get(max))
                max = word;
        }
        out.println("Student with highest login frequency :" + max + " " + st.get(max));

        // find users from lo to hi
        String lo = "dai16001";
        String hi = "dai16032";
        for(String users : st.keys(lo, hi)) {
            stud.println(users + " " + st.get(users));
        }


    }
}