using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Numerics;
using System.Text;
using System.Threading.Tasks;

namespace AtCorder
{
	public class Program
	{
		static void Main(string[] args)
		{
			var cin = new Scanner2();
			int n = cin.Int();
			int q = cin.Int();
			string s = cin.Next();
			var td = new Tuple<char, char>[q];
			for (int i = 0; i < q; i++) {
				string t = cin.Next();
				string d = cin.Next();
				td[i] = new Tuple<char, char>(t[0], d[0]);
			}

			int l = -1;
			int r = n;
			for (int i = q - 1; i >= 0; i--) {
				if (l < n) {
					if (td[i].Item1 == s[l + 1] && td[i].Item2 == 'L') {
						++l;
					} else if(l >= 0) {
						if (td[i].Item1 == s[l] && td[i].Item2 == 'R') {
							--l;
						}
					}
				}

				if (r >= 0) {
					if (td[i].Item1 == s[r - 1] && td[i].Item2 == 'R') {
						--r;
					} else if (r < n) {
						if (td[i].Item1 == s[r] && td[i].Item2 == 'L') {
							++r;
						}
					}
				}
			}

			int ans = Math.Max(0, Math.Min(r - l - 1, n));
			Console.WriteLine(ans);
		}
	}

	public class Scanner2
	{
		private readonly char[] delimiter_ = new char[] { ' ' };
		private readonly string filePath_;
		private string[] buf_;
		private int index_;
		Func<string> reader_;

		public Scanner2(string file = "")
		{
			if (string.IsNullOrWhiteSpace(file)) {
				reader_ = Console.ReadLine;
			} else {
				filePath_ = file;
				var fs = new StreamReader(file);
				reader_ = fs.ReadLine;
			}
			buf_ = new string[0];
			index_ = 0;
		}

		public string Next()
		{
			if (index_ < buf_.Length) {
				return buf_[index_++];
			}

			string st = reader_();
			while (st == "") {
				st = reader_();
			}

			buf_ = st.Split(delimiter_, StringSplitOptions.RemoveEmptyEntries);
			if (buf_.Length == 0) {
				return Next();
			}

			index_ = 0;
			return buf_[index_++];
		}

		public int Int() => 
			int.Parse(Next());
		public long Long() => long.Parse(Next());
		public double Double() => double.Parse(Next());

		public int[] ArrayInt(int N, int add = 0)
		{
			int[] Array = new int[N];
			for (int i = 0; i < N; i++) {
				Array[i] = Int() + add;
			}
			return Array;
		}

		public long[] ArrayLong(int N, long add = 0)
		{
			long[] Array = new long[N];
			for (int i = 0; i < N; i++) {
				Array[i] = Long() + add;
			}
			return Array;
		}

		public double[] ArrayDouble(int N, double add = 0)
		{
			double[] Array = new double[N];
			for (int i = 0; i < N; i++) {
				Array[i] = Double() + add;
			}
			return Array;
		}

		public void Save(string text)
		{
			if (string.IsNullOrWhiteSpace(filePath_)) {
				return;
			}

			File.WriteAllText(filePath_ + "_output.txt", text);
		}
	}
}