#include <bits/stdc++.h>

using namespace std;
using int64 = long long;
const int mod = 1e9 + 7;
const int inf = (1 << 30) - 1;
const int64 infll = (1LL << 61) - 1;

struct IoSetup {
  IoSetup() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
    cerr << fixed << setprecision(10);
  }
} iosetup;

template< typename T >
ostream &operator<<(ostream &os, const vector< T > &v) {
  for(int i = 0; i < (int) v.size(); i++) {
    os << v[i] << (i + 1 != v.size() ? " " : "");
  }
  return os;
}

template< typename T >
istream &operator>>(istream &is, vector< T > &v) {
  for(T &in : v) is >> in;
  return is;
}

template< typename T1, typename T2 >
inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }

template< typename T1, typename T2 >
inline bool chmin(T1 &a, T2 b) { return a > b && (a = b, true); }

template< typename T = int64 >
vector< T > make_v(size_t a) {
  return vector< T >(a);
}

template< typename T, typename... Ts >
auto make_v(size_t a, Ts... ts) {
  return vector< decltype(make_v< T >(ts...)) >(a, make_v< T >(ts...));
}

template< typename T, typename V >
typename enable_if< is_class< T >::value == 0 >::type fill_v(T &t, const V &v) {
  t = v;
}

template< typename T, typename V >
typename enable_if< is_class< T >::value != 0 >::type fill_v(T &t, const V &v) {
  for(auto &e : t) fill_v(e, v);
}

int main() {
  int N, Q;
  cin >> N >> Q;
  string S;
  cin >> S;
  vector< char > t(Q), d(Q);
  for(int i = 0; i < Q; i++) {
    cin >> t[i] >> d[i];
  }

  auto solve = [&](int pos, bool f) {
    int p = pos;
    for(int i = Q - 1; i >= 0; i--) {
      if(d[i] == 'L') { // ←
        if(pos + 1 < N && S[pos + 1] == t[i]) {
          ++pos;
        }
      } else {
        if(pos > 0 && S[pos - 1] == t[i]) {
          --pos;
        }
      }
      if(f) chmin(p, pos);
      else chmax(p, pos);
    }
    return p;
  };

  int L = solve(-1, false);
  int R = solve(N, true);
  cout << R - L - 1 << endl;
}