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: Accepted)

<?php
$n=trim(fgets(STDIN));
$s=trim(fgets(STDIN)) . "END";
$ans=0;
$i=0;
while($i<$n){
  if($s[$i]=="A"){
    if($s[$i+1]=="B"){
      ++$i;
      if($s[$i+1]=="C"){
        ++$i;
        ++$ans;
      }
    }
  }
  ++$i;
}
echo $ans;