PROGRAM PASC15(INPUT,OUTPUT);
LABEL 1;
VAR NUM:INTEGER;
PROCEDURE ERROR;
BEGIN
WRITELN('ERROR');
GOTO 1;
END;
BEGIN
READ(NUM);
WHILE NUM <>-1 DO
  BEGIN
  IF NUM>20 THEN ERROR;
  WRITELN(NUM);
 1:READ(NUM);
  END;
WRITELN('FINISHED');
END.