#include <bits/stdc++.h>
using namespace std;
template <typename T>
void DEBUG(T e) {
  if (true == false) return;
  std::cout << e << " ";
}
template <typename T>
void DEBUG(const std::vector<T>& v) {
  if (true == false) return;
  for (const auto& e : v) {
    std::cout << e << " ";
  }
  std::cout << std::endl;
}
template <typename T>
void DEBUG(const std::vector<std::vector<T> >& vv) {
  if (true == false) return;
  for (const auto& v : vv) {
    DEBUG(v);
  }
}
template <class T, class... Ts>
void DEBUG(T d, Ts... e) {
  if (true == false) return;
  DEBUG(d);
  DEBUG(e...);
}
template <class T>
void corner(bool flg, T hoge) {
  if (flg) {
    cout << hoge << endl;
    abort();
  }
}
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);
}
void solve(void) {
  long long N, Q;
  cin >> N;
  cin >> Q;
  string str;
  cin >> str;
  vector<pair<long long, long long> > vp;
  for (long long i = 0; i < Q; i++) {
    char X, Y;
    cin >> X >> Y;
    vp.emplace_back(X, Y);
  }
  long long L = -1, R = N;
  while (R - L > 1) {
    long long mid = (L + R) / 2;
    long long X = str[mid];
    long long P = mid;
    for (long long i = 0; i < Q; i++) {
      if (vp[i].first == X) {
        if (vp[i].second == 'L') {
          X = vp[i - 1].first;
          P--;
        } else {
          X = vp[i + 1].first;
          P++;
        }
      }
      if (P == -1 || P == N) break;
    }
    if (P == -1) {
      L = mid;
    } else {
      R = mid;
    }
  }
  long long P1 = L;
  L = -1, R = N;
  while (R - L > 1) {
    long long mid = (L + R) / 2;
    long long X = str[mid];
    long long P = mid;
    for (long long i = 0; i < Q; i++) {
      if (vp[i].first == X) {
        if (vp[i].second == 'L') {
          X = vp[i - 1].first;
          P--;
        } else {
          X = vp[i + 1].first;
          P++;
        }
      }
      if (P == -1 || P == N) break;
    }
    if (P == N) {
      R = mid;
    } else {
      L = mid;
    }
  }
  long long P2 = R;
  cout << N - P1 - 1 - (N - P2) << endl;
  return;
}
int32_t main(int32_t argc, const char* argv[]) {
  std::ios::sync_with_stdio(false);
  std::cin.tie(0);
  std::cout << std::fixed;
  std::cout << std::setprecision(11);
  solve();
  return 0;
}
