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.Linq;
using System.Collections.Generic;
using static System.Console;
using static ConsoleApp.Util;
using static System.Math;

namespace ConsoleApp
{
    class Program
    {

        static void Main(string[] args)
        {
            var n = int.Parse(ReadLine());
            var s = ReadLine();
            
            int c = 0;
            for (int i = 0; i < n-2;i++)
            {
                if(s[i] == 'A' && s[i+1] == 'B' && s[i+2 ] == 'C'){
                    c++;

                }
            }
            WriteLine(c);
        }

    }


    static class Util
    {
        public static void ChMin(ref int a, int b)
        {

            if (a > b)
            {
                a = b;
            }
        }


        public static void ChMax(ref long a, long b)
        {
            if (a < b)
            {
                a = b;
            }
        }




    }
}