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: Wrong Answer)

using System;

public class Hello{
  public static void Main(){
    int K = int.Parse(Console.ReadLine());
    char X;
    int count = 0;
    int abc = 0;
    for(int i = 0; i < K ; i++){
      X=(char)Console.Read();
      if(abc == 0 && X == ('A')){
        abc++;
      }else if(abc == 1 && X == ('B')){
        abc++;
      }else if(abc == 2 && X == ('C')){
        count++;
        abc = 0;
      }else{
        abc = 0;
      }
    }
    Console.Write(count);
  }
}