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 (GCC 5.4.1) (judge verdict: Time Limit Exceeded)

#include <stdio.h>

int main() {
  int n, a, i;
  char s[52];
  scanf("%d", &n);
  scanf("%s", s);
  a = 0;
  for(i = 0; i < n; i++){
    if(s[i] == 'A') {
      i++;
      if(i < n && s[i] == 'B') {
        i++;
        if(i < n && s[i] == 'C') {
          i++;
          a++;
        } else {
          i--;
        }
      } else {
        i--;
      }
    } else {
      i--;
    }
  }
  printf("%d\n", a);
  return 0;
}