var v:array[1..10000] of char;  {00}
f:text;
n,i,j:longint;
aux:char;
begin
assign(f,'ordine.in');reset(f);
n:=0;
while not eof(f) do
      begin
      inc(n);
      read(f,v[n]);
      end;
close(f);
for i:=1 to n-1 do
    for j:=i+1 to n do
        if ((abs(i-j)<>1) and (v[i]>v[j]) and (v[i]<>v[j-1]) and (v[i]<>v[j+1]) and (v[j]<>v[i-1]) and (v[j]<>v[i+1])) then

                        begin
                        aux:=v[i];
                        v[i]:=v[j];
                        v[j]:=aux;
                        end
        else if ((v[i]>v[j]) and (v[i]<>v[j+1]) and (v[j]<>v[i-1])) then
        begin
        aux:=v[i];
        v[i]:=v[j];
        v[j]:=aux;
        end;
assign(f,'ordine.out');rewrite(f);
for i:=1 to n do
write(f,v[i]);
close(f);
end.