http://otvet.mail.ru/question/90585465

var
  n, c, m: Integer;
  isset: Boolean;
begin
  isset := False;
  c := 1;
  m := 0;
  repeat
    write('Please, enter the ', c, 'th number or negative to exit: ');
    readln(n);
    Inc(c);
    if (n > 0) and (n mod 10 = 3) then
    begin
      if (not isset) then
        m := n
      else begin
        if (n > m) then
          m := n;
      end;
      isset := True;
    end;
  until (n < 0);
  if (isset) then
    writeln('The biggest number ended with 3 is ', m)
  else
    writeln('No number with 3 at end was found');
  readln;
end.