A1451.[COCI-2011_2012-contest4]#2 KEKS

Mirko and Slavko are bored at math class again so they came up with new game. Mirko writes down an N digit number, and Slavko’s task is to obtain the largest possible number after having removed exactly K digits.
Help him do that!

The first line of input contains integers N and K (1 ≤ K < N ≤ 500 000).
The following line contains N digit number. This number starts with non-zero digit.

The first and only line of output should contain the largest possible number Slavko can obtain by removing K digits from the given number.

In test cases worth 50% of total points, N will not exceed 1000.