let rest (r:int, b:int) =
    if (r<0 && b>0) then System.Console.WriteLine(r+b)
    elif (r<0 && b<0) then System.Console.WriteLine(r-b)
    else System.Console.WriteLine(r)
let main() =
   seq { for i in 1 .. stdin.ReadLine()|> int do yield stdin.ReadLine() }
   |> Seq.iter (fun x -> rest((x.Split(" ").[0]|>int)%(x.Split(" ").[1]|>int), (x.Split(" ").[1]|>int)))
main()