type cuvinte=array[1..1000]of string;
var s:cuvinte;
    man:string;
    i,n:longint;
    ok:boolean;
begin
assign(input,'ordine.in');reset(input);
assign(output,'ordine.out');rewrite(output);
readln(n);
 for i:=1 to n do readln(s[i]);
 repeat
     ok:=false;
     for i:=1 to n-1 do
     if s[i]>s[i+1] then begin
     man:=s[i];s[i]:=s[i+1];s[i+1]:=man;ok:=true; end;
     until not ok;
     for i:=1 to n do write(s[i]);
 close(input);close(output);
end.