(defun LevenshteinDistance (s1 s2)
  (let ((dp (make-array '(2048 2048)))
        (n (length s1))
        (m (length s2)))
    (dotimes (i (1+ n)) (setf (aref dp i 0) i))
    (dotimes (i (1+ m)) (setf (aref dp 0 i) i))
    (dotimes (i n)
      (dotimes (j m)
        (setf (aref dp (1+ i) (1+ j)) (1+ (min (aref dp i (1+ j)) (aref dp (1+ i) j)))
              (aref dp (1+ i) (1+ j)) (min (aref dp (1+ i) (1+ j)) (+ (aref dp i j) (if (char= (char s1 i) (char s2 j)) 0 1))))))
    (aref dp n m)))

(defun main (&rest argv)
  (declare (ignorable argv))
  (let* ((n (read))
         (m (read))
         (s1 (read-line))
         (s2 (read-line)))
    (declare (ignore n) (ignore m))
    (format t "~d~%" (LevenshteinDistance s1 s2))))

(main)