import java.util.Scanner;

class OneHourRank24 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        String password = sc.next();
        char a[] = password.toCharArray();
        int len = password.length();
        
        boolean check[] = new boolean[4];
        
        for(int i=0; i<4; i++) {
            check[i] = false;
        }
        
        for(int i=0; i<len; i++) {
            if((int)a[i] >= 97 && (int)a[i] <= 122) {
                check[0] = true;
            }
            else if((int)a[i] >= 65 && (int)a[i] <= 90) {
                check[1] = true;
            }
            else if((int)a[i] >= 48 && (int)a[i] <= 57) {
                check[2] = true;
            }
            else {
                check[3] = true;
            }
        }
        
        int count = 0;
        for(int i=0; i<4; i++) {
            if(check[i] == false) {
                count++;
            }
        }
        
        if(len + count <= 6) {
            System.out.println(6-len);
        } else {
            System.out.println(count);
        }
    }
}