#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main() {
  std::ios::sync_with_stdio(false), std::cin.tie(0);
  int n, q;
  cin >> n >> q;
  string s;
  cin >> s;
  vector<char> t(q);
  vector<char> d(q);
  for (int i = 0; i < q; i++) {
    cin >> t[i] >> d[i];
  }
  auto check = [&](int i) {
    for (int j = 0; j < q; j++) {
      if (s[i] == t[j]) {
        if (d[j] == 'L')
          i--;
        else
          i++;
      }
      if (i == -1 || i == n) break;
    }
    return i;
  };
  int ans = 0;
  int ok, ng;
  ok = -1, ng = n;
  while (abs(ok - ng) > 1) {
    int mid = (ok + ng) >> 1;
    if (check(mid) == -1)
      ok = mid;
    else
      ng = mid;
  }
  ans = ok + 1;
  ok = n, ng = -1;
  while (abs(ok - ng) > 1) {
    int mid = (ok + ng) >> 1;
    if (check(mid) == n)
      ok = mid;
    else
      ng = mid;
  }
  ans += n - ok;
  cout << n - ans << endl;
  return 0;
}
