B. Deleting Letters from the SMS
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output

Pedro wants to send an SMS to his parents. Since he doesn't have much balance left, he has decided to eliminate spaces. By doing this, he has a message of $$$n$$$ letters, but he only has enough balance to pay for $$$k$$$ letters, with $$$k \leq n$$$.

Pedro wants to delete letters, without altering the order of the others, in such a way that the final message is the lexicographically smallest possible with $$$k$$$ letters.

Given $$$n$$$, $$$k$$$, and the message, help Pedro reduce the message.

Input

The input starts with an integer $$$t$$$, the number of cases. Each case consists of a line with the integers $$$n$$$ and $$$k$$$, followed by another line with the original message of $$$n$$$ letters, all of which are lowercase.

Output

For each case, write a line with the final message.

Scoring

$$$1 \leq k \leq n \leq 100000$$$

$$$t \leq 100$$$

1 point: $$$k = n$$$

3 points: $$$k = 1$$$

5 points: $$$k = 2$$$

10 points: $$$k \leq 10$$$

3 points: $$$k = n-1$$$

5 points: $$$k = n-2$$$

10 points: $$$k \geq n-10$$$

30 points: $$$n \leq 100$$$

33 points: $$$n \leq 100000$$$

Example
Input
4
4 1
yxwv
9 8
tqbjtqmif
10 5
eatqvgjpog
10 8
tpoudnqtob
Output
v
qbjtqmif
agjog
oudnqtob