In this Kata, you will be given two integers `n` and `k` and your task is to remove `k-digits` from `n` and return the lowest number possible, without changing the order of the digits in `n`. Return the result as a string.
Let's take an example of `solve(123056,4)`. We need to remove `4` digits from `123056` and return the lowest possible number. The best digits to remove are `(1,2,3,6)` so that the remaining digits are `'05'`. Therefore, `solve(123056,4) = '05'`. 
Note also that the order of the numbers in `n` does not change: `solve(1284569,2) = '12456',` because we have removed `8` and `9`. 
More examples in the test cases.
Good luck!
from itertools import combinations

def solve(n, k):
    s = str(n)
    return ''.join(min(xs for xs in combinations(s, len(s)-k)))
from itertools import combinations

def solve(n, k):
    s = str(n)
    return ''.join(min(xs for xs in combinations(s, len(s)-k)))