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 Ruby (2.3.3) (judge verdict: Accepted)

def printer(n, s, v)
  abc_index = s.index('ABC')
  return v if abc_index == nil
  s[abc_index, 3] = 'ZZZ'
  next_abc_index = s.index('ABC')
  return v+1 if next_abc_index == nil
  printer(n, s, v+1)
end
n = gets.chop.split.map(&:to_i)
s = gets.chop
print printer(n, s, 0)