open System
let rec f n res =
  if n = 0 then res else f (n - 1) (List.append res [Console.ReadLine()])
  
let tmp = Array.map int (Console.ReadLine().Split(' '))
let lst = f tmp.[0] []
let s_lst = List.sort lst
Console.WriteLine (List.fold (fun acc x -> acc + x) "" s_lst)
