Amicable numbers

(*
    This program computes the amicable numbers within the range from
    "ug" (lower limit) to "og" (upper limit), to compile run "fpc befr_zahlen.pas".
    (The method used in this program is rather simplistic.)
    Copyright (C) <March 19th, 2015> Henning POLZER, h underscore polzer at gmx dot de

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*)


PROGRAM befreundete_zahlen;
VAR hilf, j, ug, og: longword;              (* Standard: integer *)

FUNCTION ts (z: longword): longword;            (* Teilersumme berechnen *)
VAR i, gegenteiler, schleife, summe: longword;

BEGIN
  schleife := z;
  i := 2;
  summe := 1;
  REPEAT
    gegenteiler := trunc (schleife / i);
    IF schleife MOD i = 0 THEN
      IF i = gegenteiler THEN summe := summe + i    (* Teiler = Gegenteiler? Nur Teiler beachten! *)
      ELSE summe := summe + gegenteiler + i;
    i := i + 1
  UNTIL gegenteiler < i;
  ts := summe
END;

BEGIN
  REPEAT
    writeln ('Befreundete Zahlen finden, zum Beenden fuer mind. einen Wert 0 eingeben:');
    write ('Untergrenze: '); readln (ug);
    write ('Obergrenze : '); readln (og);

    IF (ug > 0) AND (og > 0) THEN
      FOR j := ug TO og DO
      BEGIN
        hilf := ts (j);
        IF hilf <> j THEN
          IF (ts (hilf) = j) AND (hilf > j) THEN writeln (j:10, ' und ', hilf:10) (* formatierte Ausgabe *)
      END (* FOR *)
  UNTIL (ug = 0) OR (og = 0)
END.