var a:array[1..100] of longint;
n,i,j:longint;
x:char;
f,g:text;
begin
assign(f,'ordine.in');reset(f);
assign(g,'ordine.out');rewrite(g);
while not eof(f) do
  while not eoln(f) do begin
  read(f,x);
  a[ord(x)-96]:=a[ord(x)-96]+1;
end;
for i:=1 to 32 do
  for j:=1 to a[i] do
    write(g,chr(ord(i+96)));
close(g);
end.