public static String getSmallestAndLargest(String s, int k) {
        String smallest = "";
        String largest = "";
        
        // Complete the function
        // 'smallest' must be the lexicographically smallest substring of length 'k'
        // 'largest' must be the lexicographically largest substring of length 'k'
        
        int start = 0;
        smallest = s.substring(start, k); //give a starting point of the first 3 characters
        largest = s.substring(start, k);
        while((start + k) <= s.length()){
            
            String Temp = s.substring(start, start+k);
            smallest = (smallest.compareTo(Temp) > 0) ? Temp : smallest;
            largest = (largest.compareTo(Temp) < 0) ? Temp : largest;
            start++;
        }
        
        return smallest + "\n" + largest;
    }