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

int check(char c)
{
    int res=0;
    string numbers = "0123456789";
    string lower_case = "abcdefghijklmnopqrstuvwxyz";
    string upper_case = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    string special_characters = "!@#$%^&*()-+";
    for(size_t i=0; i<numbers.size(); i++){
        if (c==numbers[i])
            return 0x01;
    }
    for(size_t i=0; i<lower_case.size(); i++){
        if (c==lower_case[i])
            return 0x02;
    }
    for(size_t i=0; i<upper_case.size(); i++){
        if (c==upper_case[i])
            return 0x04;
    }
    for(size_t i=0; i<special_characters.size(); i++){
        if (c==special_characters[i])
            return 0x08;
    }
    return res;
}

int count(int n){
    int res=0;
    int flag=1;
    for(int i=0; i<4; i++, flag*=2){
        cerr << "checking n: " << n << " and " << flag;
        if(n&flag){
            res++;
        }
        cerr << ", res = " << res << endl;
    }
    return res;
}

int minimumNumber(int n, string password) {
    // Return the minimum number of characters to make the password strong
    int flags=0;
    for(int i=0; i<n; i++){
        flags |= check(password[i]);
    }
    cerr << "flags: " << flags << endl;
    int c = count(flags);
    cerr << "count : " << c << endl;
    int requisites = 4-c;
    return max(requisites, 6-(int)password.length());
}

int main() {
    int n;
    cin >> n;
    string password;
    cin >> password;
    int answer = minimumNumber(n, password);
    cout << answer << endl;
    return 0;
}