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

int main(){
  int n;
  string s;
  cin >> n >> s;
  
  int count = 0;
  for(int i = 0; i < n-2; i++){
    if(s.substr(i,3) == "ABC")
    	++count;
  }
  cout << count;
}