program ordine;
var i,n:integer;
    a:char;
    ok:boolean;
    v:string;
    f,g:text;
begin
    assign(f,'ordine.in');
    reset(f);
    assign(g,'ordine.out');
    rewrite(g);
    readln(f,v);
    n:=length(v);
    ok:=true;
    while ok=true do
       begin
          ok:=false;
          for i:=1 to n-1 do
               if ord(v[i])>ord(v[i+1]) then
                  begin
                     a:=v[i];
                     v[i]:=v[i+1];
                     v[i+1]:=a;
                     ok:=true;
                   end;
         end;
    ok:=true;
    while ok=true do
       begin
          ok:=false;
          for i:=2 to n-1 do
               if ord(v[i])=ord(v[i-1]) then
                  begin
                     a:=v[i];
                     v[i]:=v[i+1];
                     v[i+1]:=a;
                     ok:=true;
                   end;
         end;
    for i:=1 to n do
        write(g,v[i]);
    writeln(g);
    close(f);close(g);
end.