#include <bits/stdc++.h>
using namespace std;
inline bool EQ(double a, double b) { return fabs(a - b) < 1e-9; }
template <typename T>
inline T gcd(T a, T b) {
  if (b == 0)
    return a;
  else
    return gcd(b, a % b);
}
template <typename T>
inline T lcm(T a, T b) {
  return (a * b) / gcd(a, b);
}
template <typename T>
string toStr(T x) {
  stringstream st;
  st << x;
  string s;
  st >> s;
  return s;
}
template <class T>
void splitStr(const string &s, vector<T> &out) {
  istringstream in(s);
  out.clear();
  copy(istream_iterator<T>(in), istream_iterator<T>(), back_inserter(out));
}
inline int two(int n) { return 1 << n; }
inline int isOnBit(int n, int b) { return (n >> b) & 1; }
inline void onBit(int &n, int b) { n |= two(b); }
inline void offBit(int &n, int b) { n &= ~two(b); }
inline int lastBit(int n) { return n & (-n); }
inline int cntBit(int n) {
  int res = 0;
  while (n && ++res) n -= n & (-n);
  return res;
}
const int dx4[] = {-1, 0, 1, 0};
const int dy4[] = {0, 1, 0, -1};
const int dx8[] = {-1, 0, 1, 0, -1, -1, 1, 1};
const int dy8[] = {0, 1, 0, -1, -1, 1, -1, 1};
long long gcd(long long a, long long b) {
  if (a == 0) return b;
  return gcd(b % a, a);
}
long long modexp(long long x, long long y, long long p) {
  long long res = 1;
  x = x % p;
  while (y > 0) {
    if (y & 1) res = (res * x) % p;
    y = y >> 1;
    x = (x * x) % p;
  }
  return res;
}
long long n, q;
string s;
vector<pair<char, char>> v;
long long checkleft(long long x) {
  long long cur = x;
  for (long long i = 0, _n = (q); i < _n; i++) {
    if (s[cur] == v[i].first) {
      if (v[i].second == 'R') {
        cur++;
      } else {
        cur--;
      }
      if (cur == -1)
        return 1;
      else if (cur == n)
        return 0;
    }
  }
  return 0;
}
long long checkright(long long x) {
  long long cur = x;
  for (long long i = 0, _n = (n); i < _n; i++) {
    if (s[cur] == v[i].first) {
      if (v[i].second == 'R') {
        cur++;
      } else {
        cur--;
      }
      if (cur == n)
        return 1;
      else if (cur == -1)
        return 0;
    }
  }
  return 0;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout << setprecision(11);
  cin >> n >> q;
  cin >> s;
  for (long long i = 0, _n = (q); i < _n; i++) {
    char a, b;
    cin >> a >> b;
    v.push_back(make_pair(a, b));
  }
  long long l = 0, r = n - 1;
  long long ans1 = -1;
  long long ans2 = n;
  while (l <= r) {
    long long mid = (l + r) / 2;
    if (checkleft(mid)) {
      ans1 = max(ans1, mid);
      l = mid + 1;
    } else {
      r = mid - 1;
    }
  }
  l = 0, r = n - 1;
  while (l <= r) {
    long long mid = (l + r) / 2;
    if (checkright(mid)) {
      ans2 = min(ans2, mid);
      r = mid - 1;
    } else {
      l = mid + 1;
    }
  }
  cout << ans2 - ans1 - 1;
}
