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 Java (OpenJDK 11.0.6) (judge verdict: Wrong Answer)

import java.util.*;
 
class Main{
  public static void main(String[] args){
    Scanner ISR = new Scanner(System.in);
    int N = ISR.nextInt();
    String St = ISR.next();
    int R = 0;
    for(int i = 0;i<N;i++){
      if(i<N-2&&St.substring(i,i+1).equals("A")){
        i++;
        if(St.substring(i,i+1).equals("B")){
          i++;
          if(St.substring(i,i+1).equals("C")){
            R++;
          }
        }
      }
    }
    System.out.println(R);
  }
}