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++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;

int main(){
  ll n,i,j,ans;
  j=1;
  ans=0;
  string s,t;
  char* a[4];
  a[1]="A";
  a[2]="B";
  a[3]="C";
  cin >> n >> s;
  for(i=1;i<=n;i++){
    t=s.substr(0,1);
    s.erase(0,1);
    if(a[j]==t){
      if(j==3){
        ans+=1;
        j=1;
      }
      else{
        j+=1;
      }
    }
    else{
      j=1;
    }
  }
  cout << ans;
}