public static String pangrams(String s) {
    // Write your code here
        var letters = s.chars()
            .filter(c -> Character.isAlphabetic(c))
            .map(c -> Character.toLowerCase(c))
            .mapToObj(c -> c)
            .collect(Collectors.toSet());
        
        return letters.size() == 26 ? "pangram" : "not pangram";