Problem:
Score : 200 points

Problem Statement

We have a string S of length N consisting of uppercase English letters.

How many times does ABC occur in S as contiguous subsequences (see Sample Inputs and Outputs)?

Constraints

3 \leq N \leq 50

S consists of uppercase English letters.

Input

Input is given from Standard Input in the following format:

N
S

Output

Print number of occurrences of ABC in S as contiguous subsequences.

Sample Input 1

10
ZABCDBABCQ

Sample Output 1

2

Two contiguous subsequences of S are equal to ABC: the 2-nd through 4-th characters, and the 7-th through 9-th characters.

Sample Input 2

19
THREEONEFOURONEFIVE

Sample Output 2

0

No contiguous subsequences of S are equal to ABC.

Sample Input 3

33
ABCCABCBABCCABACBCBBABCBCBCBCABCB

Sample Output 3

5

Solution in Common Lisp (SBCL 1.1.14) (judge verdict: Accepted)

(defun split (delimiter target-string)
  (let ((delimiter-position (search delimiter target-string))
        (delimiter-size (length delimiter)))
    (if delimiter-position
        (cons (subseq target-string 0 delimiter-position)
              (split delimiter (subseq target-string (+ delimiter-position delimiter-size))))
        (list target-string))))

(let ((n (read))
      (l (split "ABC" (read-line))))
  (princ (- (length l) 1)))