/*
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*/
/**
*
* @author Dell
*/
import java.util.*;
public class SubStringProblem {
public static void getSmallestAndLargest(String s , int k){
java.util.ArrayList atr = new java.util.ArrayList();
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);
}
}