How can I get a repdigit? In honor of how much rep I had several hours ago, when I first thought of this challenge:

Numbers like this that are made up of a single digit repeating are called repdigits. Repdigits are fun! Every body would be more happy if the amount of rep they had was a repdigit¹, but I am impatient, so you need to help me find out the fastest way to get to a repdigit.
Here is your challenge:
Given a positive integers representing reputation, output the minimum amount of rep they need to gain to get to a repdigit. For example, at the time of writing this challenge, user Martin Ender had 102,856 rep. The nearest rep-digit is 111,111, so he would need to gain: 8255 rep to be at a repdigit.
Since people dislike losing rep, we will only consider non-negative changes. This means that, for example, if someone is at 12 rep, rather than losing 1 rep, the solution is to gain 10 rep. This allows '0' to be a valid output, since anyone who has 111 rep is already at a repdigit.
Input and output can be in any reasonable format, and since it is impossible to have less than 1 rep on any Stack Exchange site, you can assume no inputs will be less than 1.
One cornercase to note:
If a user has less than 10 rep, they are already at a repdigit, and so they also need '0'.
Test IO:
#Input      #Ouput
8           0
100         11
113         109
87654321    1234567
42          2
20000       2222
11132       11090

Standard loopholes apply, and the shortest solution in bytes wins!
Haskell, 39 bytes
until(((==).head&gt;&gt;=all).show)(+1)&gt;&gt;=(-)

Try it online