; (setq numbers '(1 15 7 3 8 8 19 5 12 8 2 6 8))
(setq numbers '(1 15 8 8 8 8 7 3 19 5 12 2 6))

(setq counter 1)
(if (> (list-length numbers) 0) 
    (progn (setq prev (car numbers)) 
           (setq numbers (cdr numbers))))

(loop
    while (and (> (list-length numbers) 0) (< counter 4))
    do
        (setq next (car numbers))
        (setq numbers (cdr numbers))
        (if (eql prev next) 
            (setq counter (+ counter 1))
            (progn (setq counter 1) (setq prev next))))

(if (eql counter 4)
    (print "Found four times repeated number")
    (print "No four times repeated number found"))