Mirko and Slavko are bored at math class again so they came up with new game. Mirko writes down an digit number, and Slavko's task is to obtain the largest possible number after having removed exactly digits.
Help him do that!
Input Specification
The first line of input contains integers and .
The following line contains digit number. This number starts with non-zero digit.
Output Specification
The first and only line of output should contain the largest possible number Slavko can obtain by removing digits from the given number.
Scoring
In test cases worth of total points, will not exceed .
Sample Input 1
4 2
1924
Sample Output 1
94
Sample Input 2
7 3
1231234
Sample Output 2
3234
Sample Input 3
10 4
4177252841
Sample Output 3
775841
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