import java.io.*;
import java.math.*;
import java.security.KeyStore.Entry;
import java.util.*;

class SPOJANDCC
{
	private InputStream is;
	private PrintWriter out;

	void solve()
	{
		String num = "0123456789", low = "abcdefghijklmnopqrstuvwxyz", upp = "ABCDEFGHIJKLMNOPQRSTUVWXYZ",
				spe = "!@#$%^&*()-+";
		ni();
		String a = ns();
		int b[] = new int[4];
		for (int i = 0; i < a.length(); i++)
		{
			if (num.contains("" + a.charAt(i)))
				b[0]++;
			else if (low.contains("" + a.charAt(i)))
				b[1]++;
			else if (upp.contains("" + a.charAt(i)))
				b[2]++;
			else if (spe.contains("" + a.charAt(i)))
				b[3]++;
		}
		int min = Math.max(0, 6 - a.length());
		int tmp = 0;
		for (int i = 0; i < 4; i++)
			if (b[i] == 0)
				tmp++;
		min = Math.max(tmp, min);
		out.println(min);
	}

	void soln()
	{
		is = System.in;
		out = new PrintWriter(System.out);
		solve();
		out.flush();
	}

	public static void main(String[] args)
	{
		new Thread(null, new Runnable()
		{
			public void run()
			{
				try
				{
					new SPOJANDCC().soln();
				} catch (Exception e)
				{
					e.printStackTrace();
				}
			}
		}, "1", 1 << 26).start();
	}

	// To Get Input
	// Some Buffer Methods
	private byte[] inbuf = new byte[1024];
	public int lenbuf = 0, ptrbuf = 0;

	private int readByte()
	{
		if (lenbuf == -1)
			throw new InputMismatchException();
		if (ptrbuf >= lenbuf)
		{
			ptrbuf = 0;
			try
			{
				lenbuf = is.read(inbuf);
			} catch (IOException e)
			{
				throw new InputMismatchException();
			}
			if (lenbuf <= 0)
				return -1;
		}
		return inbuf[ptrbuf++];
	}

	private boolean isSpaceChar(int c)
	{
		return !(c >= 33 && c <= 126);
	}

	private int skip()
	{
		int b;
		while ((b = readByte()) != -1 && isSpaceChar(b))
			;
		return b;
	}

	private double nd()
	{
		return Double.parseDouble(ns());
	}

	private char nc()
	{
		return (char) skip();
	}

	private String ns()
	{
		int b = skip();
		StringBuilder sb = new StringBuilder();
		while (!(isSpaceChar(b)))
		{ // when nextLine, (isSpaceChar(b) && b != '
			// ')
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}

	private char[] ns(int n)
	{
		char[] buf = new char[n];
		int b = skip(), p = 0;
		while (p < n && !(isSpaceChar(b)))
		{
			buf[p++] = (char) b;
			b = readByte();
		}
		return n == p ? buf : Arrays.copyOf(buf, p);
	}

	private char[][] nm(int n, int m)
	{
		char[][] map = new char[n][];
		for (int i = 0; i < n; i++)
			map[i] = ns(m);
		return map;
	}

	private int[] na(int n)
	{
		int[] a = new int[n];
		for (int i = 0; i < n; i++)
			a[i] = ni();
		return a;
	}

	private int ni()
	{
		int num = 0, b;
		boolean minus = false;
		while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
			;
		if (b == '-')
		{
			minus = true;
			b = readByte();
		}

		while (true)
		{
			if (b >= '0' && b <= '9')
			{
				num = num * 10 + (b - '0');
			} else
			{
				return minus ? -num : num;
			}
			b = readByte();
		}
	}

	private long nl()
	{
		long num = 0;
		int b;
		boolean minus = false;
		while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
			;
		if (b == '-')
		{
			minus = true;
			b = readByte();
		}

		while (true)
		{
			if (b >= '0' && b <= '9')
			{
				num = num * 10 + (b - '0');
			} else
			{
				return minus ? -num : num;
			}
			b = readByte();
		}
	}
}