#include <bits/stdc++.h>
using namespace std;
const int P = 1e9 + 7, INF = 0x3f3f3f3f;
long long gcd(long long a, long long b) { return b ? gcd(b, a % b) : a; }
long long qpow(long long a, long long n) {
  long long r = 1 % P;
  for (a %= P; n; a = a * a % P, n >>= 1)
    if (n & 1) r = r * a % P;
  return r;
}
long long inv(long long first) {
  return first <= 1 ? 1 : inv(P % first) * (P - P / first) % P;
}
inline int rd() {
  int first = 0;
  char p = getchar();
  while (p < '0' || p > '9') p = getchar();
  while (p >= '0' && p <= '9') first = first * 10 + p - '0', p = getchar();
  return first;
}
const int N = 1e6 + 10;
int n, m, vis[N], f[N], g[N];
char s[N];
int main() {
  scanf("%d%d%s", &n, &m, s);
  for (int i = 1; i <= m; ++i) vis[rd()] = 1;
  int len = strlen(s), j = 0;
  for (int i = 1; i <= len - 1; ++i) {
    while (j && s[i] != s[j]) j = f[j];
    if (s[i] == s[j]) ++j;
    f[i + 1] = j;
  }
  for (j = f[len]; j; j = f[j]) g[j] = 1;
  int ans = 1, now = 0;
  for (int i = 1; i <= n; ++i) {
    if (!vis[i]) {
      if (!now || i - now >= len) ans = (long long)ans * 26 % P;
    } else {
      if (now && i - now < len && !g[now + len - i]) ans = 0;
      now = i;
    }
  }
  printf("%d\n", ans);
}
