#include <bits/stdc++.h>

using namespace std;

int minimumNumber(int n, string password) {
    // Return the minimum number of characters to make the password strong
    vector<int>a(4,0);
    for(int i=0;i<n;i++){
        if(password[i]>='a'&&password[i]<='z')
            a[0]=1;
        else if(password[i]>='A'&&password[i]<='Z')
            a[1]=1;
        else if(password[i]>='0'&&password[i]<='9')
            a[2]=1;
        else
            a[3]=1;
    }
    int count=0;
    for(int i=0;i<4;i++){
        if(a[i]==0)
            count++;
    }
    if(n>=6)
        return count;
    int size=n+count;
    if(size>=6)
        return count;
    else
        return 6-n;
}

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