/*

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*/

/**

*

* @author Dell

*/

import java.util.*;

public class SubStringProblem {

public static void getSmallestAndLargest(String s , int k){

java.util.ArrayList<String> atr = new java.util.ArrayList<String>();

for(int i = 0 ; i < s.length() - (k - 1); i++){

String sp = "";

for(int j = i ; j < i + k ; j++){

sp = sp + s.charAt(j);

}

// System.out.println(sp);

atr.add(sp);

}

Collections.sort(atr);

System.out.println(atr.get(0) +"\n"+atr.get(atr.size()-1));

}

public static void main(String[] args){

Scanner sc = new Scanner(System.in);

String s = sc.nextLine();

int k = sc.nextInt();

getSmallestAndLargest(s,k);

}

}