(defvar n)
(defvar SS)
(defvar TT)
(defvar cnt)

(read-line)
(setq SS (read-line))
(setq TT (read-line))
(setq cnt 0)
(loop for i from 0 to (- (length SS) 1) do
        (values)
        (if (eql (aref SS i) (aref TT i)) (values) (incf cnt))
)
(format t "~d~%" cnt)