% Calculates n!

PROCEDURE m;
   VAR s, n;

   PROCEDURE f;
      VAR m;
   BEGIN
      ASSIGN n > m;
      IF m - 2 THEN
         ASSIGN n -1 > n;
         CALL f;
         ASSIGN s * m > s;
      FI;

      IF 1 - m THEN
         ASSIGN 1 > s;
      FI;
   END;

BEGIN
   INPUT n;
   CALL f;
   OUTPUT s;
END;