#include<iostream>
#include<string>
using namespace std;

int main() {
	int n;
	string s;
	cin >> n >> s;
	int res = 0;
	for(int i = 0; i <= n - 3; i++) {
		if (s.substr(i, 3) == "ABC")
			res++;
	}
	cout << res;
}