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)

// template.cpp

// Defines.
//#define DEBUG
#define NUMBER_OF_DIGITS 6

// Includes.
#include <bits/stdc++.h>

#ifdef DEBUG
#include <chrono>
#endif

// Usings.
using namespace std;

// Main function.
int main()
{
#ifdef DEBUG
	chrono::system_clock::time_point start, end;
	
	start = chrono::system_clock::now();
#endif
	
	// settings.
	ios::sync_with_stdio(false);
	
	//cout << fixed;
	//cout << setprecision(NUMBER_OF_DIGITS);
	
	// logic.
	int n;
	cin >> n;
	string s;
	cin >> s;
	
	int counter = 0;
	for (int i = 0; i < (n - 2); i++)
	{
		if ((s[i] == 'A') && (s[i + 1] == 'B') && (s[i + 2] == 'C'))
		{
			counter++;
		}
	}
	cout << counter << endl;

#ifdef DEBUG
	end = chrono::system_clock::now();
	
	double elapsed = chrono::duration_cast<std::chrono::milliseconds>(end-start).count();
	cout << elapsed << "[ms]" << endl;
#endif
	
	return 0;
}