import java.io.*;
class strong
{
	public static void main(String args[])throws IOException
	{
		try
		{
			BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
			int n=Integer.parseInt(br.readLine());
			String str=br.readLine();
			int a[]=new int[4];
			int k=0,f=0;
			for(int i=0;i<n;i++)
			{
				char ch=str.charAt(i);
				int asc=(int)ch;
				if(ch=='!'||ch=='@'||ch=='#'||ch=='$'||ch=='%'||ch=='^'||ch=='&'||ch=='*'||ch=='('||ch==')'||ch=='-'||ch=='+')
				{
					a[0]++;
				}
				if(asc>=48&&asc<=57)
				{
					a[1]++;
				}
				if(asc>=65&&asc<=90)
				{
					a[2]++;
				}
				if(asc>=97&&asc<=122)
				{
					a[3]++;
				}
			}
			for(int i=0;i<4;i++)
			{
				if(a[i]>0)
				{
					k++;
				}
			}
			if(n<6)
			{
				if(6-n>4-k)
				{
					f=6-n;
				}
				else
				{
					f=4-k;
				}
			}
			else
			{
				f=4-k;
			}
			System.out.println(f);
		}
		catch(Exception ex)
		{
			return;
		}
	}
}