import java.io.*;
import java.util.*;
import java.math.*;
// import java.awt.Point;
 
public class Main {
    InputStream is;
    PrintWriter out;
    String INPUT = "";
 
    static int mod = 1_000_000_007;
    // int mod = 998244353;
    long inf = Long.MAX_VALUE/2;

    void solve(){
        int n = ni();
        int q = ni();
        char[] s = ns().toCharArray();
        int[][] val = new int[q][2];
        for(int i = 0; i < q; i++){
            String[] tmp = ns().split(" ");
            val[i][0] = tmp[0].charAt(0)-'A';
            val[i][1] = tmp[1].charAt(0)=='L' ? -1 : 1;
        }
        int left = -1;
        int right = n;
        int ans = 0;
        while(right-left>1){
            int mid = (left+right)/2;
            if(left_flow(n,mid,s,val,q)) left = mid;
            else right = mid;
        }
        ans += left+1;
        left = -1;
        right = n;
        while(right-left>1){
            int mid = (left+right)/2;
            if(right_flow(n,mid,s,val,q)) right = mid;
            else left = mid;
        }
        ans += (n-right);
        out.println(Math.max(0,n-ans));
    }

    boolean left_flow(int n, int c, char[] s, int[][] val, int q){
        int cur = c;
        int p = s[cur]-'A';
        for(int i = 0; i < q; i++){
            if(val[i][0]==p){
                cur += val[i][1];
                if(cur<0) return true;
                if(cur>=n) return false;
                p = s[cur]-'A';
            }
        }
        return false;
    }

    boolean right_flow(int n, int c, char[] s, int[][] val, int q){
        int cur = c;
        int p = s[cur]-'A';
        for(int i = 0; i < q; i++){
            if(val[i][0]==p){
                cur += val[i][1];
                if(cur>=n) return true;
                if(cur<0) return false;
                p = s[cur]-'A';
            }
        }
        return false;
    }

    void run() throws Exception
    {
        is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes());
        out = new PrintWriter(System.out);
        long s = System.currentTimeMillis();
        solve();
        out.flush();
        if(!INPUT.isEmpty())tr(System.currentTimeMillis()-s+"ms");
    }
    
    public static void main(String[] args) throws Exception { new Main().run(); }
    
    private byte[] inbuf = new byte[1024];
    private 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) && 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();
        }
    }
    
    private static void tr(Object... o) { System.out.println(Arrays.deepToString(o)); }
 
}


Measured memory_bytes: 66556