import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;
import java.util.StringTokenizer;
 
 public class Main {
   public static void main(String[] args) throws IOException {
     BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
     int n = Integer.parseInt(in.readLine());
     StringTokenizer stk = new StringTokenizer(in.readLine());
     in.close();
     String s = stk.nextToken();
     int diff = s.replaceAll("ABC","").length();
     System.out.println((n-diff)/3);
   }
 }
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz