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)

n = gets.chomp.to_i
#k,x = gets.chomp.split().map(&:to_i)

s = gets.chomp.split(//)

ans = 0
count = 0
s.each do |c|
  if c == 'A'
    count = 1
  elsif c == 'B' && count == 1
    count = 2
  elsif c == 'C' && count == 2
    ans += 1
    count = 0
  else
    count = 0
  end
end

puts ans