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 Haskell (GHC 7.10.3) (judge verdict: Accepted)

main :: IO()
main = do
  n <- readLn :: IO Int
  str <- getLine
  let times = findSubStr str
  print times
  where
    findSubStr :: String -> Int
    findSubStr [] = 0
    findSubStr (s:ss) = findABC str + findSubStr ss
      where
        str = [s]++ss
        substr (list) 0 m = take m list
        substr (l:ls) n m = substr ls (n - 1) m
        findABC :: String -> Int
        findABC [] = 0
        findABC str = if (substr str 0 3 == "ABC") then 1 else 0