[YVitaliy]

Код:

procedure TForm1.Button1Click(Sender: TObject);
var value,ovalue,c:Integer;
o:byte;
th: set of 0..9;
begin
  th:=[];
  value:=strtointdef(edit1.Text,0);
  c:=0;
    while (value>0) and (c<=2) do begin
    ovalue:=value;
    value:=value div 10;
    o:=ovalue-value*10;
      if not(o in th)  then inc(c);
      th:=th+[o];
    end;
  if c<=2 then
  showmessage('Двоякое') else
  showmessage('Недвоякое');
end;