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 OCaml (4.10.0) (judge verdict: Accepted)

let count_ABC str sz =
  let rec iter_count pos rest =
    if pos >= sz - 2
    then rest
    else 
      if String.sub str pos 3 = "ABC"
      then iter_count (pos+1) (rest+1)
      else iter_count (pos+1) rest
  in iter_count 0 0

let () = Scanf.scanf "%d\n %s" @@ fun n s -> Printf.printf "%d\n" @@ count_ABC s n