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 PHP7 (7.0.15) (judge verdict: Wrong Answer)

<?php
  $n = trim(fgets(STDIN));
  $s = trim(fgets(STDIN));
  $count = 0;
  for($i=1; $i<strlen($s)-1; $i++){
    if ($s[$i-1] == "A" && 
        $s[$i]-1 == "B" && 
        $s[$i+1] == "C"){
      $count++;
    }
  }
  echo $count."\n";
  ?>