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;
class Program
{
  static void Main(string[] args)
  {
    // 整数の入力
    int n = int.Parse(Console.ReadLine());
    
    // スペース区切りの整数の入力
    string input = Console.ReadLine();
    char[] chararray = input.ToCharArray(); 

    int result = 0;

    for(int i=0; i < n-2; i++){
      if(chararray[i] == 'A'){
        if(chararray[i+1] == 'B'){
          if(chararray[i+2] == 'C'){
            result++;
          }
        }
      }
    }
  
    //出力
    Console.WriteLine(result);
  }
}