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 Python (3.4.3) (judge verdict: Accepted)

str = input()
a = str.split(" ")
n = (int)(a[0])
k = (int)(a[1])
str = input()
before = ""
for ii in range(k-1):
  s = str + str[::-1]
  s1 = s[0:n]
  for i in range(1,n+1):
    s2 = s[i:n+i]
    if(s1>s2):
      s1 = s2
  str = s1[::-1]
  if(before==str):
    break
  before = str

s = str + str[::-1]
s1 = s[0:n]
for i in range(1,n+1):
  s2 = s[i:n+i]
  if(s1>s2):
    s1 = s2
print(s1)