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# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;

class Program
{
	static void Main(string[] args)
	{
		int N = int.Parse(Console.ReadLine());
		string S = Console.ReadLine();
		int cnt = 0;
		for(int i = 0;i < N - 2; i++)
        {
			if ("ABC" == S.Substring(i, 3))
				cnt++;
        }
		Console.WriteLine(cnt);
	}
}


//string s = Console.ReadLine();
//int[] intArray = Console.ReadLine().Split(' ').Select(i => int.Parse(i)).ToArray();
//int H = intArray[0];
//int W = intArray[1];
//int N = int.Parse(Console.ReadLine());
//List<int> A = new List<int>(Console.ReadLine().Split(' ').Select(i => int.Parse(i)).ToArray());
//Boolean ok = false;

//Console.WriteLine(ans);
//Console.WriteLine("Yes");
//Console.WriteLine("No");
//Console.ReadKey();
//Console.WriteLine(cnt);

//string[] strArray = Console.ReadLine().Split(' ').ToArray();
//string S = strArray[0];
//string T = strArray[1];