import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.StringTokenizer;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        FastScanner in = new FastScanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        C_SnukeTheWizard solver = new C_SnukeTheWizard();
        solver.solve(1, in, out);
        out.close();
    }

    static class C_SnukeTheWizard {
        public void solve(int testNumber, FastScanner in, PrintWriter out) {
            int n = in.nextInt();
            int q = in.nextInt();
            char[] s = in.next().toCharArray();
            int[] dir = new int[q];
            char[] let = new char[q];
            for (int i = 0; i < q; i++) {
                let[i] = in.next().charAt(0);
                dir[i] = in.next().equals("L") ? -1 : +1;
            }

            int l = -1;
            int r = n;
            while (r - l > 1) {
                int m = (l + r) / 2;
                int p = m;
                for (int i = 0; i < q; i++) {
                    if (let[i] == s[p]) {
                        p += dir[i];
                    }
                    if (p < 0 || p >= n) {
                        break;
                    }
                }
                if (p < 0) {
                    l = m;
                } else {
                    r = m;
                }
            }
            int L = l;

            l = -1;
            r = n;
            while (r - l > 1) {
                int m = (l + r) / 2;
                int p = m;
                for (int i = 0; i < q; i++) {
                    if (let[i] == s[p]) {
                        p += dir[i];
                    }
                    if (p < 0 || p >= n) {
                        break;
                    }
                }
                if (p >= n) {
                    r = m;
                } else {
                    l = m;
                }
            }
            int R = r;

            out.println(R - L - 1);
        }

    }

    static class FastScanner {
        private BufferedReader in;
        private StringTokenizer st;

        public FastScanner(InputStream stream) {
            in = new BufferedReader(new InputStreamReader(stream));
        }

        public String next() {
            while (st == null || !st.hasMoreTokens()) {
                try {
                    String rl = in.readLine();
                    if (rl == null) {
                        return null;
                    }
                    st = new StringTokenizer(rl);
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return st.nextToken();
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }

    }
}



Measured memory_bytes: 47584