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: Accepted)

#include <cstdio>
#include <cstring>

#define MAX_N	51
/* -----------------------------------------------------------------------------
	型とクラス定義
----------------------------------------------------------------------------- */

/* -----------------------------------------------------------------------------
	大域データ
----------------------------------------------------------------------------- */
int 	N;			// 文字列長
char S[MAX_N];	// 文字列

int main () {

	int cnt = 0;

	// 個数と長さの読込み
	scanf("%d %s", &N, S);

	//
	for(int i = 0; i < N; i++) 
		if(strncmp(S+i, "ABC", 3) == 0) cnt++;

	printf("%d\n", cnt);

	return 0;
}