import java.io.*;
import java.util.Locale;
import java.util.StringTokenizer;

public class TaskB {
    private final InputReader reader;
    private final OutputWriter writer;

    public TaskB(InputReader reader, OutputWriter writer) {
        this.reader = reader;
        this.writer = writer;
    }

    public static void main(String[] args) {
        InputReader reader = new InputReader(System.in);
        OutputWriter writer = new OutputWriter(System.out);
        new TaskB(reader, writer).run();
        writer.writer.flush();
    }

    public void run() {
        int n = reader.nextInt();
        int m = reader.nextInt();
        char[] S = reader.next().toCharArray();
        int k = S.length;
        int[] P = new int[k + 1];
        P[0] = P[1] = 0;
        for (int i = 2; i <= k; i++) {
            P[i] = 0;
            for (int p = P[i - 1]; p != 0; p = P[p])
                if (S[p] == S[i - 1]) {
                    P[i] = p + 1;
                    break;
                }
            if (P[i] == 0 && S[i - 1] == S[0])
                P[i] = 1;
        }
        boolean[] good = new boolean[k + 1];
        good[0] = true;
        for (int p = k; p != 0; p = P[p])
            good[p] = true;
        int end = 0;
        int ans = 1;
        final int MOD = 1000 * 1000 * 1000 + 7;
        for (int i = 0; i < m; i++) {
            int x = reader.nextInt();
            if (x > end) {
                for (int j = 0; j < x - end - 1; j++)
                    ans = (int)((ans * 1l * 26) % MOD);
            } else {
                if (!good[end - x + 1])
                    ans = 0;
            }
            end = x + k - 1;
        }
        while (end < n) {
            ans = (int) ((ans * 1l * 26) % MOD);
            end++;
        }
        writer.printf("%d\n", ans);
    }


    static class InputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            tokenizer = null;
        }

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

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

        public double nextDouble() {
            return Double.parseDouble(next());
        }

        public long nextLong() {
            return Long.parseLong(next());
        }
    }

    static class OutputWriter {
        public PrintWriter writer;

        OutputWriter(OutputStream stream) {
            writer = new PrintWriter(stream);
        }

        public void printf(String format, Object... args) {
            writer.print(String.format(Locale.ENGLISH, format, args));
        }
    }
}