import java.util.Scanner;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    sc.nextLine();
    char[] S = sc.nextLine().toCharArray();
    Main abc150B = new Main();
    System.out.println(abc150B.solve(S));
  }

  public Integer solve(char[] S){
    Integer ret = 0;
    char[] a = {'A', 'B', 'C'};
    int ai = 0;
    for(int i = 0; i < S.length; i++ ){
      if(S[i] != a[ai]) {
        ai = 0;
      }
      if(S[i] == a[ai]) {
        ai++;
        if(ai >= a.length) {
          ret += 1;
          ai = 0;
        }
      } 
    }
    return ret;
  }
}

/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