import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.math.BigDecimal;
import java.util.AbstractMap;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.Deque;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Queue;
import java.util.Set;
import java.util.TreeSet;
import static java.util.Comparator.*;				

public class Main {
	
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        MyInput in = new MyInput(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        
        Solver solver = new Solver();
        solver.solve(1, in, out);
        
        out.close();
    }
    
    // ======================================================================
    // 1 <= T <= 100 : 問題の数
    // 1 <= |Si} <= 100 : 文字列 
    //
    // １つの文字列を分割して TOKYO または　KYOTO を含む文字列を最大いくつ作れるか？
    // 
    // 
    //
    static class Solver {

    	int[] BAN = null;
    	Map<String, List<Integer>> mapL = new HashMap<String, List<Integer>>();
    	Map<String, List<Integer>> mapR = new HashMap<String, List<Integer>>();
    	
    	public void solve(int testNumber, MyInput in, PrintWriter out) {
        	int ans = 0;
       		int N = in.nextInt();
       		BAN = new int[N];
       		Arrays.fill(BAN, 1);
       		int Q = in.nextInt();
       		String S = in.nextString();
       		List<Integer> list = null;
       		for(int i=0; i < S.length(); i++) {
       			list = mapL.get(String.valueOf(S.charAt(i)));
       			if(list == null) {
       			  //  out.println(" [" + String.valueOf(S.charAt(i)) + "]  list == null ");
       				list = new ArrayList<Integer>();
       				mapL.put(String.valueOf(S.charAt(i)), list);
       			}
       			list.add(i);
       		}
       		List<Integer> list2 = null;
       		for(String key : mapL.keySet()) {
       			list = mapL.get(key);
       			list2 = new ArrayList<>(list);
       			list2.sort(reverseOrder());
       			mapR.put(key, list2);
//       		    out.println("key = " + key + "  L [" + list + "]");
//       		    out.println("key = " + key + "  R [" + list2 + "]");
       		}
       		String C = null;
       		String LR = null;
       		ans = N;
       		for(int i=0; i < Q; i++) {
       			C = in.nextString();
       			LR = in.nextString();
//    			out.println("  [" + C + "] --> [" + LR + "]");
       			if(LR.equals("L")) {
       				list = mapL.get(C);
       				if(list == null) {
       				    continue;
       				 //   out.println("list = null !!!");
       				}
       				for(Integer ii : list) {
       					if(ii == 0) {
       	       				ans -= BAN[0];
       	       				BAN[0] = 0;
//       	       				out.println("BAN[0] = " + BAN[0]);
       	       			} else {
       						BAN[ii -1] += BAN[ii];
       						BAN[ii] = 0;
//       	       				out.println("L   BAN[" + (ii -1) + "] = " + BAN[ii-1]);
//       	       				out.println("L   BAN[" + ii + "] = " + BAN[ii]);
       					}
       				}
       			} else {
       				list = mapR.get(C);
       				if(list == null) {
       				    continue;
       				 //   out.println("list = null !!!");
       				}
       				for(Integer ii : list) {
       					if(ii == (N-1)) {
       	       				ans -= BAN[N-1];
       	       				BAN[N-1] = 0;
//       	       				out.println("R   BAN[" + (N - 1) + "] = " + BAN[N - 1]);
       					} else {
       						BAN[ii+1] += BAN[ii];
       						BAN[ii] = 0;
//       	       				out.println("R   BAN[" + (ii +1) + "] = " + BAN[ii+1]);
//       	       				out.println("R   BAN[" + ii + "] = " + BAN[ii]);
       					}
       				}
       			}
//       			for(int iii = 0 ; iii < N; iii++) 
//       			    out.print("[" + BAN[iii] + "]");
//       			out.println("  ans = " + ans);
       		}
       		out.println(ans);
        }
    }
    // ======================================================================
    static class Pair<K, V> extends AbstractMap.SimpleEntry<K, V> {
        /** serialVersionUID. */
        private static final long serialVersionUID = 6411527075103472113L;

        public Pair(final K key, final V value) {
            super(key, value);
        }
     }    
    static class MyInput {
        private final BufferedReader in;
        private static int pos;
        private static int readLen;
        private static final char[] buffer = new char[1024 * 8];
        private static char[] str = new char[500 * 8 * 2];
        private static boolean[] isDigit = new boolean[256];
        private static boolean[] isSpace = new boolean[256];
        private static boolean[] isLineSep = new boolean[256];
 
        static {
            for (int i = 0; i < 10; i++) {
                isDigit['0' + i] = true;
            }
            isDigit['-'] = true;
            isSpace[' '] = isSpace['\r'] = isSpace['\n'] = isSpace['\t'] = true;
            isLineSep['\r'] = isLineSep['\n'] = true;
        }
 
        public MyInput(InputStream is) {
            in = new BufferedReader(new InputStreamReader(is));
        }
 
        public int read() {
            if (pos >= readLen) {
                pos = 0;
                try {
                    readLen = in.read(buffer);
                } catch (IOException e) {
                    throw new RuntimeException();
                }
                if (readLen <= 0) {
                    throw new MyInput.EndOfFileRuntimeException();
                }
            }
            return buffer[pos++];
        }
 
        public int nextInt() {
            int len = 0;
            str[len++] = nextChar();
            len = reads(len, isSpace);
            int i = 0;
            int ret = 0;
            if (str[0] == '-') {
                i = 1;
            }
            for (; i < len; i++) ret = ret * 10 + str[i] - '0';
            if (str[0] == '-') {
                ret = -ret;
            }
            return ret;
        }
 
        public long nextLong() {
            int len = 0;
            str[len++] = nextChar();
            len = reads(len, isSpace);
            int i = 0;
            long ret = 0L;
            if (str[0] == '-') {
                i = 1;
            }
            for (; i < len; i++) ret = ret * 10 + str[i] - '0';
            if (str[0] == '-') {
                ret = -ret;
            }
            return ret;
        }
 
       public String nextString() {
        	String ret = new String(nextDChar()).trim();
            return ret;
        }
 
        public char[] nextDChar() {
            int len = 0;
            len = reads(len, isSpace);
            char[] ret = new char[len + 1];
            for (int i=0; i < len; i++)		ret[i] = str[i];
            ret[len] = 0x00;
            return ret;
        }
 
        public char nextChar() {
            while (true) {
                final int c = read();
                if (!isSpace[c]) {
                    return (char) c;
                }
            }
        }
 
        int reads(int len, boolean[] accept) {
            try {
                while (true) {
                    final int c = read();
                    if (accept[c]) {
                        break;
                    }
                    if (str.length == len) {
                        char[] rep = new char[str.length * 3 / 2];
                        System.arraycopy(str, 0, rep, 0, str.length);
                        str = rep;
                    }
                    str[len++] = (char) c;
                }
            } catch (MyInput.EndOfFileRuntimeException e) {
            }
            return len;
        }
 
        static class EndOfFileRuntimeException extends RuntimeException {
        }
    }
}
