Number Reduction
Description
You are given a positive integer $x$.
You can apply the following operation to the number: remove one occurrence of any digit in such a way that the resulting number does not contain any leading zeroes and is still a positive integer. For example, $10142$ can be converted to $1142$, $1042$, $1012$ or $1014$ (note that $0142$ is not a valid outcome); $10$ can be converted to $1$ (but not to $0$ since it is not positive).
Your task is to find the minimum positive integer that you can obtain from $x$ if you can apply the aforementioned operation exactly $k$ times.
The first line contains a single integer $t$ ($1 \le t \le 10^5$) — the number of test cases.
The first line of each test case contains a single integer $x$ ($1 \le x < 10^{500000}$).
The second line contains a single integer $k$ ($0 \le k < |x|$), where $|x|$ is the length of the number $x$.
The sum of $|x|$ over all test cases does not exceed $5 \cdot 10^5$.
For each test case, print one integer — the minimum positive number that you can obtain from $x$ if you can apply the operation exactly $k$ times.
Input
The first line contains a single integer $t$ ($1 \le t \le 10^5$) — the number of test cases.
The first line of each test case contains a single integer $x$ ($1 \le x < 10^{500000}$).
The second line contains a single integer $k$ ($0 \le k < |x|$), where $|x|$ is the length of the number $x$.
The sum of $|x|$ over all test cases does not exceed $5 \cdot 10^5$.
Output
For each test case, print one integer — the minimum positive number that you can obtain from $x$ if you can apply the operation exactly $k$ times.
5
10000
4
1337
0
987654321
6
66837494128
5
7808652
3
1
1337
321
344128
7052