var v:array [1..1000] of char;
    f,g:text;
    f1:boolean;
    aux:char;
    n,i,j,k:word;
begin
     assign(f,'ordine.in');
     reset(f);
     assign(g,'ordine.out');
     rewrite(g);
     i:=0;
     while eoln(f)=false do
           begin
                i:=i+1;
                read(f,v[i]);
           end;
     n:=i;


     i:=2;
     while i<n-1 do
           begin
           j:=i;
                if v[j]=v[j-1] then
                   begin
                        f1:=true;
                        k:=1;
                        while f1=true do
                              begin
                                   if (v[j+k]<>v[j]) and (v[j+k+1]<>v[j]) then
                                      begin
                                           aux:=v[j];
                                           v[j]:=v[j+k];
                                           v[j+k]:=aux;
                                           f1:=false;
                                      end else k:=k+1;
                              end;
                    end;
           i:=i+1;
           end;
     i:=n-1;
     while i>1 do
           begin
           j:=i;
                if v[j]=v[j+1] then
                   begin
                        f1:=true;
                        k:=1;
                        while f1=true do
                              begin
                                   if (v[j-k]<>v[j]) and (v[j-k-1]<>v[j]) then
                                      begin
                                           aux:=v[j];
                                           v[j]:=v[j-k];
                                           v[j-k]:=aux;
                                           f1:=false;
                                      end else k:=k+1;
                              end;
                    end;
           i:=i-1;
           end;
     for i:=1 to n do
         write(g,v[i]);
     close(f);
     close(g);
end.