import java.util.Scanner;

public class Solution {

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 stpsize=1;
    int n=s.length()-k+1;
    String []res=new String[n];
    for(int i=0;i<n;i++)
        res[i]=s.substring(i,i+k);

     for (int i = 0; i < res.length - 1; i++) {
        for (int j = 0; j < res.length - i - 1; j++) {
            if (res[j].compareTo(res[j + 1]) > 0) {
                String temp = res[j];
                res[j] = res[j + 1];
                res[j + 1] = temp;
            }
        }
    }
    smallest=res[0];
    largest=res[res.length - 1];
    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));
}

}