import java.util.*;
class Solution
{
    static int minimumNumber(int n, String s)
    {
        boolean flag[] = new boolean[4];
        for(int i=0;i<n;i++)
        {
            boolean t=false;
            int c = (int)s.charAt(i);
            if(c>=(int)'a' && c<=(int)'z')
                flag[0]=t=true;
            if(c>=(int)'A' && c<=(int)'Z')
                flag[1]=t=true;
            if(c>=(int)'0' && c<=(int)'9')
                flag[2]=t=true;
            if(!t)
                flag[3]=true;
        }
        int k=0;
        for(int i=0;i<4;i++)
            if(!flag[i])
                k++;
        return (6-n)>k?(6-n):k;
    }
    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();
    }
}