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with Ada.Text_Io;
procedure Twice is
begin
   for I in 10..10000 loop
      declare
         Str:String:=Integer'Image(I);
         Num:Natural:=Natural'Value("13#"&Str(Str'First+1..Str'Last)&"#");
      begin
         if Num=I*2 then
            Ada.Text_Io.Put_Line(Integer'Image(I)&" => "&Integer'Image(Num));
         end if;
      end;
   end loop;
end Twice;