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 Java7 (OpenJDK 1.7.0) (judge verdict: Accepted)

import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        String S = sc.next();

        int count = 0;
        boolean a = false;
        boolean b = false;
        boolean c = false;
        for (int i = 0; i < N; i++) {
            String s = S.charAt(i) + "";
            if (s.equals("A")) {
                a = true;
                b = false;
                c = false;
            } else if (s.equals("B") && a && !b && !c) {
                b = true;
                c = false;
            } else if (s.equals("C") && a && b && !c) {
                c = true;
                count++;
            } else {
                a = false;
                b = false;
                c = false;
            }
        }

        System.out.println(count);
        sc.close();
    }
}