public static string pangrams(string s)
    {
        s = s.ToLower();
        
        int[] alphabet = new int[26];
        
        foreach(char c in s){
            if(c >= 'a' && c <='z'){
                alphabet[(int)c - (int)'a']++;
            }
        }

        return alphabet.Any(c => c == 0) ? "not pangram" : "pangram";
    }