Problem:
Score : 300 points

Problem Statement

You are given a string s.
Among the different substrings of s, print the K-th lexicographically smallest one.

A substring of s is a string obtained by taking out a non-empty contiguous part in s.
For example, if s = ababc, a, bab and ababc are substrings of s, while ac, z and an empty string are not.
Also, we say that substrings are different when they are different as strings.

Let X = x_{1}x_{2}...x_{n} and Y = y_{1}y_{2}...y_{m} be two distinct strings. X is lexicographically larger than Y if and only if Y is a prefix of X or x_{j} > y_{j} where j is the smallest integer such that x_{j} \neq y_{j}.

Constraints

1 ≤ |s| ≤ 5000

s consists of lowercase English letters.

1 ≤ K ≤ 5

s has at least K different substrings.

Partial Score

200 points will be awarded as a partial score for passing the test set satisfying |s| ≤ 50.

Input

Input is given from Standard Input in the following format:

s
K

Output

Print the K-th lexicographically smallest substring of K.

Sample Input 1

aba
4

Sample Output 1

b

s has five substrings: a, b, ab, ba and aba.
Among them, we should print the fourth smallest one, b.
Note that we do not count a twice.

Sample Input 2

atcoderandatcodeer
5

Sample Output 2

andat

Sample Input 3

z
1

Sample Output 3

z

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Runtime Error)

import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.List;
import java.util.StringTokenizer;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.Vector;

public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        TaskB solver = new TaskB();
        solver.solve(1, in, out);
        out.close();
    }

    static class TaskB {
        public static int n;
        public static int[] flags;
        public static Vector<Vector<Integer>> graph;
        public static void flag(int v , int f){
            flags[v] = f;
            for (int i = 0; i <graph.get(v).size() ; i++){
                if (flags[graph.get(v).get(i)] == 0) flag(graph.get(v).get(i) , f );
            }
        }
        public void solve(int testNumber, InputReader in, PrintWriter out) {

            n = in.nextInt();
            int m = in.nextInt();
             flags = new int[n+1];
            int[]ind= new int[n+1];
            graph = new Vector<>(n+1);
            for (int i = 0; i <n+1 ; i++) {
                graph.add(new Vector<>(n+1));
            }
            for (int i = 1; i <=n ; i++) {
                ind[in.nextInt()] = i;
            }
            for (int i = 0; i <m ; i++) {
                int v = in.nextInt(),u=in.nextInt();
                graph.get(v).add(u);
                graph.get(u).add(v);
            }
            int f ;
            for (int i = 1; i <=n; i++) {
                f = i;
                if (flags[i] == 0){
                    flag(i ,f);
                }
            }
            int ans = 0;
            for (int i = 1; i <=n ; i++) {
                if (i != ind[i]){
                    if (flags[i] == flags[ind[i]]) ans++;
                }
                else ans++;
            }
            out.println(ans);








        }
    }

    static class InputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            tokenizer = null;
        }

        public String next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }

        public long nextLong() {
            return Long.parseLong(next());
        }

    }
}