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)

$debug = false
flag = ARGV.shift
if flag == "-d"
  $debug = true
end

def dputs str
  p str if $debug
end

def max(n, m)
  if n > m
    return n
  else
    return m
  end
end

def min(n, m)
  if n < m
    return n
  else
    return m
  end
end

def gets_all_int
  return gets.chomp.split.map{|v| v.to_i}
end

## start
N = gets.to_i
S = gets.strip
ABC="ABC"

cnt = 0
0.upto(S.length - ABC.length) do |i|
  if S[i,3] == ABC
    cnt += 1
  end
end
puts cnt