#include <bits/stdc++.h>
using namespace std;
const char sp = ' ';
const char cmm = ',';
const int MOD = 1000000007;
using ll = long long;
ll mod(ll a, ll b) { return (a % b + b) % b; }
ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
ll lcm(ll a, ll b) { return a * b / gcd(a, b); }
void Yes() { cout << "Yes" << endl; }
void No() { cout << "No" << endl; }
void Judge(bool b) { b ? Yes() : No(); }
void YES() { cout << "YES" << endl; }
void NO() { cout << "NO" << endl; }
void JUDGE(bool b) { b ? YES() : NO(); }
ll powMod(ll b, ll e, ll m) {
  ll r = 1;
  while (e > 0) {
    if (e & 1) r = (r % m) * (b % m) % m;
    b = (b % m) * (b % m) % m;
    e >>= 1;
  }
  return r;
}
double distance(ll x1, ll y1, ll x2, ll y2) {
  return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
}
template <typename T>
void ppp(T n) {
  cout << n << endl;
}
template <typename T1, typename T2>
ostream& operator<<(ostream& s, const pair<T1, T2>& p) {
  return s << "(" << p.first << ", " << p.second << ")";
}
template <typename T>
ostream& operator<<(ostream& s, const vector<T>& v) {
  int len = v.size();
  cout << '[';
  for (int i = 0; i < len; ++i) {
    s << v[i];
    if (i < len - 1) s << ", ";
  }
  cout << ']';
  return s;
}
int n, q;
string s;
vector<pair<char, char>> mov;
int check(int x) {
  char now = s[x];
  for (auto inst : mov) {
    char t = inst.first;
    char d = inst.second;
    if (t != now) continue;
    if (d == 'R')
      ++x;
    else
      --x;
    if (x < 0)
      return 1;
    else if (x >= n)
      return -1;
    now = s[x];
  }
  return 0;
}
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cin >> n >> q;
  cin >> s;
  mov.resize(q);
  for (int i = 0; i < (q); ++i) {
    char t, d;
    cin >> t >> d;
    mov[i] = make_pair(t, d);
  }
  int ok = n;
  int ng = -1;
  while (ok - ng > 1) {
    int mid = ng + (ok - ng) / 2;
    if (check(mid) == 0) {
      ok = mid;
    } else {
      ng = mid;
    }
  }
  int left = ok;
  ng = n;
  ok = -1;
  while (ng - ok > 1) {
    int mid = ok + (ng - ok) / 2;
    if (check(mid) == 0) {
      ok = mid;
    } else {
      ng = mid;
    }
  }
  int right = ng;
  cerr << left << sp << right << endl;
  ppp(right - left);
  return 0;
}
