import java.util.Scanner;

public class Solution {

public static String getSmallestAndLargest(String s, int k) {
    String smallest = s.substring(0,k);
    String largest = smallest;

    int index = k;

    while(index <= s.length()){

        if(smallest.compareTo(s.substring(index-k,index)) > 0){
            smallest = s.substring(index-k,index);
        }

        if(largest.compareTo(s.substring(index-k,index)) < 0){
            largest = s.substring(index-k,index);
        }

        index += 1;

    }

    // Complete the function
    // 'smallest' must be the lexicographically smallest substring of length 'k'
    // 'largest' must be the lexicographically largest substring of length 'k'

    return smallest + "\n" + largest;
}


public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);
    String s = scan.next();
    int k = scan.nextInt();
    scan.close();

    System.out.println(getSmallestAndLargest(s, k));
}

}