import java.util.Scanner;

public class Solution { static String getSmallestAndLargest(String s, int k) { String smallest = s.substring(0,k); String largest = s.substring(0,k); for(int i=1;i<=s.length()-k;i++){ String sub = s.substring(i,i+k); int d = smallest.compareTo(sub); if(d>0) smallest = sub; String new_sub = s.substring(i,i+k); int p = largest.compareTo(new_sub); if(p<0) largest = new_sub;

      }

    // 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));
}

}