import java.util.*;
public class Main {
	public static void main(String[] args){
    	Scanner sc = new Scanner(System.in);
      	
      	int n = sc.nextInt();
      	String s = sc.next();
      	String ref = "ABC";
      	int sum = 0;
      
      	for (int i = 0; i + 2 < n; i++){
        	if (ref.equals(s.substring(i, i+3)))
            	sum++;
        }
      	
      	System.out.println(sum);
    }
}

/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