import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    static int minimumNumber(int n, String p) {
        // Return the minimum number of characters to make the password strong
        int sln=0,dn=0,cn=0,sn=0,i;
        char []c=p.toCharArray();
        for(i=0;i<n ;i++){
            if(c[i]>=97 && c[i]<123){
                sn++;
            }
            else if(c[i]>=65 && c[i]<=90)
                cn++;
            else if(c[i]>='0' && c[i]<='9')
                dn++;
            else if(c[i]=='!' || c[i]=='@'||c[i]=='#'||c[i]=='$'||c[i]=='%'||c[i]=='^'||c[i]=='&'||c[i]=='*'||c[i]==40||c[i]==41||c[i]=='-'||c[i]=='+' )
                sln++;
        if(sln>0 && sn>0 && dn>0 && cn>0)
            i=n;
        }
        int an=0;
        if(sn==0)
            an++;
        if(sln==0)
            an++;
        if(dn==0)
            an++;
        if(cn==0)
            an++;
        if(n<6){
            int x=6-n;
            if(x>an)
                an=x;
               }
        return an;
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        String password = in.next();
        int answer = minimumNumber(n, password);
        System.out.println(answer);
        in.close();
    }
}