Problem:
Score : 1300 points

Problem Statement

Takahashi has a string S of length N consisting of lowercase English letters.
On this string, he will perform the following operation K times:

Let T be the string obtained by reversing S, and U be the string obtained by concatenating S and T in this order.

Let S' be some contiguous substring of U with length N, and replace S with S'.

Among the strings that can be the string S after the K operations, find the lexicographically smallest possible one.

Constraints

1 \leq N \leq 5000

1 \leq K \leq 10^9

|S|=N

S consists of lowercase English letters.

Input

Input is given from Standard Input in the following format:

N K
S

Output

Print the lexicographically smallest possible string that can be the string S after the K operations.

Sample Input 1

5 1
bacba

Sample Output 1

aabca

When S=bacba, T=abcab, U=bacbaabcab, and the optimal choice of S' is S'=aabca.

Sample Input 2

10 2
bbaabbbaab

Sample Output 2

aaaabbaabb

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)

import java.util.Arrays;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner scan = new Scanner(System.in);

		//文字列の長さ
		int n = scan.nextInt();
		//繰り返す回数
		int k = scan.nextInt();
		//文字列
		String s = scan.next();
		String[] ss = new String[n];
		String[] tt = new String[n];
		String[] uu = new String[n+1];

		for(int ii=0;ii<k;ii++) {
			for(int i=0;i<n;i++) {
				ss[i] = s.substring(i, i+1);
			}

			for(int i=0;i<(n+1)/2;i++) {
				tt[i] = ss[n-i-1];
				tt[n-i-1] = ss[i];
			}

			for(int i=0;i<n;i++) {
				s = s.concat(tt[i]);
			}

			for(int i=0;i<n+1;i++) {
				uu[i] = s.substring(i, i+n);
			}
			Arrays.sort(uu);
			s = uu[0];
		}
		System.out.println(uu[0]);

	}

}