var
 a:array[0..1100]of string;
 i,j,k,l,m,n:longint;

begin
 assign(input,'brick.in');reset(input);
 assign(output,'brick.out');rewrite(output);
 readln(n);
 for i:=1 to n do readln(a[i]);
 
 for i:=1 to n do
  for j:=1 to n-1 do
   if a[j]+a[j+1]<a[j+1]+a[j] then
    begin
     a[0]:=a[j];a[j]:=a[j+1];a[j+1]:=a[0];
    end;
 for i:=1 to n do write(a[i]);
 writeln;
 close(input);close(output);
end.