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: Accepted)

#include <stdio.h>
int main() {
  int N, i, count, num;
  count = num = 0;
  scanf("%d", &N);
  char S[N];
  scanf("%s", S);
  for (i = 0; i < N; ++i) {
    if (S[i] == 'A') {
      num = 1;
    } else if (num == 1 && S[i] == 'B') {
      num = 2;
    } else if (num == 2 && S[i] == 'C') {
      ++count;
      num = 0;
    } else {
      num = 0;
    }
  }
  
  printf("%d\n", count);
  return 0;
}