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 (2.7.1) (judge verdict: Accepted)

#!/usr/bin/env ruby
# require 'pry'

# N
# a_1 b_1
# ...
# a_N b_N
# ↑を[[a_1,..a_N],[b_1,..b_N]]にする
# N = gets.to_i
# a, b = N.times.map{gets.split.map(&:to_i)}.transpose

n = gets.to_i
s = gets.chomp.split('')
abc = ['A','B','C']
count = 0
(n-2).times do |i|
  3.times do |j|
    break if s[i+j] != abc[j]
    count += 1 if j == 2
  end
end
puts count