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 C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <iostream>
#include <string>

using namespace std;

int main()
{
	int N, flag, count = 0;
	string S;

	cin >> N ;
	cin >> S;

	for (int i = 0; i < N; i++) {
		if (S[i] == 'A')
			flag = 1;
		else if (S[i] == 'B' && flag == 1)
			flag = 2;
		else if (S[i] == 'C' && flag == 2)
			flag = 3;
		else
			flag = 0;

		if (flag == 3) {
			flag = 0;
			count++;
		}
	}

	cout << count;
}