#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int N, Q;
  cin >> N >> Q;
  string S;
  cin >> S;
  char t[N], d[N];
  int ts = -1, te = N;
  for (int i = 0; i < Q; i++) {
    cin >> t[i] >> d[i];
  }
  for (int i = Q - 1; i >= 0; i--) {
    if (te - ts <= 1) break;
    if (d[i] == 'L') {
      if (ts < N - 1 && S[ts + 1] == t[i]) ts++;
      if (te < N && S[te] == t[i]) te++;
    } else if (d[i] == 'R') {
      if (0 <= ts && S[ts] == t[i]) ts--;
      if (0 < te && S[te - 1] == t[i]) te--;
    }
  }
  cout << N - (ts + 1 + N - te) << endl;
  return 0;
}
