public static String pangrams(String s) {
    // Write your code here
        String alpha = "abcdefghijklmnopqrstuvwxyz";
        Set<Character> alphaSet = alpha.chars()
                                    .mapToObj(c -> (char)c)
                                    .collect(Collectors.toSet());
        Set<Character> givenSet = s.replaceAll("\\s", "").toLowerCase().chars()
                                    .mapToObj(c -> (char)c)
                                    .collect(Collectors.toCollection(TreeSet::new));
        return givenSet.equals(alphaSet) ? "pangram" : "not pangram";       
    }