#include <bits/stdc++.h>

using namespace std;

int minimumNumber(int n, string password) {
    // Return the minimum number of characters to make the password strong
   int i;
    int found1=0,found2=0,found3=0,found4=0;
    for(i=0;i<n;i++){
        if(password[i]>='0' && password[i]<='9')
            found1++;
        else if(password[i]>='A' && password[i]<='Z')
            found2++;
        else if(password[i]>='a' && password[i]<='z')
            found3++;
        else
            found4++;
    }
    int r1=0,r2=0,r3=0,r4=0;
    if(found1==0){
        r1=1;
    }
    if(found2==0){
        r2=1;
    }
    if(found3==0){
        r3=1;
    }
    if(found4==0){
        r4=1;
    }
    if(r1+r2+r3+r4+n >=6)
        return r1+r2+r3+r4;
    else
        return 6-n;
}

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