var     a:array[0..1010]of string;
        n,m,i,j:longint;
        s:string;

procedure init;
begin
        readln(n);
        for i:=1 to n do readln(a[i]);
end;

procedure work;
begin
        for i:=1 to n do
                for j:=i+1 to n do if a[i]+a[j]<a[j]+a[i] then
                begin
                        s:=a[i]; a[i]:=a[j]; a[j]:=s;
                end;
        for i:=1 to n do write(a[i]);
end;

begin
assign(input,'brick.in');reset(input);
assign(output,'brick.out');rewrite(output);
        init;
        work;
close(output);
end.