#include <bits/stdc++.h>
using namespace std;
template <class T>
inline bool chmax(T& a, T b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T>
inline bool chmin(T& a, T b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T1, class T2>
ostream& operator<<(ostream& s, pair<T1, T2> P) {
  return s << '<' << P.first << ", " << P.second << '>';
}
template <class T>
ostream& operator<<(ostream& s, vector<T> P) {
  for (long long i = 0; i < P.size(); ++i) {
    if (i > 0) {
      s << " ";
    }
    s << P[i];
  }
  return s;
}
template <class T>
ostream& operator<<(ostream& s, vector<vector<T> > P) {
  for (long long i = 0; i < P.size(); ++i) {
    s << endl << P[i];
  }
  return s << endl;
}
template <class T>
ostream& operator<<(ostream& s, set<T> P) {
  for (__typeof__((P).begin()) it = (P).begin(); it != (P).end(); ++it) {
    s << "<" << *it << "> ";
  }
  return s << endl;
}
template <class T1, class T2>
ostream& operator<<(ostream& s, map<T1, T2> P) {
  for (__typeof__((P).begin()) it = (P).begin(); it != (P).end(); ++it) {
    s << "<" << it->first << "->" << it->second << "> ";
  }
  return s << endl;
}
template <class T>
void show(vector<T> v) {
  for (long long i = 0; i < v.size(); i++) {
    cerr << v[i] << " ";
  }
  cerr << "\n";
}
string t;
long long d[200010];
long long n, q;
string s;
bool left(long long p) {
  for (long long i = 0; i < q; i++) {
    if (s[p] - 'A' == t[i] - 'A') {
      p += d[i];
      if (p < 0) return true;
      if (p >= n) return false;
    }
  }
  return false;
}
bool right(long long p) {
  for (long long i = 0; i < q; i++) {
    if (s[p] - 'A' == t[i] - 'A') {
      p += d[i];
      if (p >= n) return true;
      if (p < 0) return false;
    }
  }
  return false;
}
signed main() {
  cin >> n >> q;
  cin >> s;
  for (long long i = 0; i < q; i++) {
    cin >> t[i];
    char x;
    cin >> x;
    if (x == 'L')
      d[i] = -1;
    else
      d[i] = 1;
  }
  long long ret = n;
  long long l = -1, r = n;
  while (r - l > 1) {
    long long mid = l + (r - l) / 2;
    if (left(mid))
      l = mid;
    else
      r = mid;
  }
  ret -= l;
  l = -1, r = n;
  while (r - l > 1) {
    long long mid = l + (r - l) / 2;
    if (right(mid))
      r = mid;
    else
      l = mid;
  }
  ret -= n - l;
  cout << ret << endl;
  return 0;
}
