#include <bits/stdc++.h>
using namespace std;
long long int mpow(long long int a, long long int b) {
  if (b == 0)
    return 1;
  else if (b % 2 == 0) {
    long long int memo = mpow(a, b / 2);
    return memo * memo % (long long int)(1e9 + 7);
  } else
    return mpow(a, b - 1) * a % (long long int)(1e9 + 7);
}
long long int lpow(long long int a, long long int b) {
  if (b == 0)
    return 1;
  else if (b % 2 == 0) {
    long long int memo = lpow(a, b / 2);
    return memo * memo;
  } else
    return lpow(a, b - 1) * a;
}
long long int gcd(long long int a, long long int b) {
  if (b == 0)
    return a;
  else
    return gcd(b, a % b);
}
vector<long long int> kaijo_memo;
long long int kaijo(long long int n) {
  if (kaijo_memo.size() > n) return kaijo_memo[n];
  if (kaijo_memo.size() == 0) kaijo_memo.push_back(1);
  while (kaijo_memo.size() <= n)
    kaijo_memo.push_back(kaijo_memo[kaijo_memo.size() - 1] * kaijo_memo.size() %
                         (long long int)(1e9 + 7));
  return kaijo_memo[n];
}
vector<long long int> gyaku_kaijo_memo;
long long int gyaku_kaijo(long long int n) {
  if (gyaku_kaijo_memo.size() > n) return gyaku_kaijo_memo[n];
  if (gyaku_kaijo_memo.size() == 0) gyaku_kaijo_memo.push_back(1);
  while (gyaku_kaijo_memo.size() <= n)
    gyaku_kaijo_memo.push_back(
        gyaku_kaijo_memo[gyaku_kaijo_memo.size() - 1] *
        mpow(gyaku_kaijo_memo.size(), (long long int)(1e9 + 7) - 2) %
        (long long int)(1e9 + 7));
  return gyaku_kaijo_memo[n];
}
long long int nCr(long long int n, long long int r) {
  if (n == r) return 1;
  if (n < r || r < 0) return 0;
  long long int ret = 1;
  ret *= kaijo(n);
  ret %= (long long int)(1e9 + 7);
  ret *= gyaku_kaijo(r);
  ret %= (long long int)(1e9 + 7);
  ret *= gyaku_kaijo(n - r);
  ret %= (long long int)(1e9 + 7);
  return ret;
}
vector<int> G[1002];
int main(void) {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  cout << fixed << setprecision(15);
  long long int n, q;
  cin >> n >> q;
  string s;
  cin >> s;
  vector<char> T(q);
  vector<char> D(q);
  for (int i = 0; i < (int)(q); i++) {
    cin >> T[i] >> D[i];
  }
  long long int L = -1, R = n;
  long long int l = -1, r = n;
  for (int i = q - 1; i >= 0; i--) {
    if (D[i] == 'L') {
      if (l + 1 < n && s[l + 1] == T[i]) l = min(n, l + 1);
      if (r + 1 <= n && s[r] == T[i]) r = min(n, r + 1);
    } else {
      if (l - 1 >= -1 && s[l] == T[i]) l = max(-1ll, l - 1);
      if (r - 1 >= 0 && s[r - 1] == T[i]) r = max(-1ll, r - 1);
    }
    L = (((L) < (l)) ? (l) : (L));
    R = (((R) > (r)) ? (r) : (R));
  }
  cout << R - L - 1 << endl;
  return 0;
}
