#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize("Ofast,03")
#pragma comment(linker, "/stack:200000000")
#pragma GCC target("avx,avx2,fma")
#pragma GCC optimization("unroll-loops")
void fio() {}
template <typename T>
void TIME(T start, T end) {}
void __print(int x) { cerr << x; }
void __print(long x) { cerr << x; }
void __print(long long x) { cerr << x; }
void __print(unsigned x) { cerr << x; }
void __print(unsigned long x) { cerr << x; }
void __print(unsigned long long x) { cerr << x; }
void __print(float x) { cerr << x; }
void __print(double x) { cerr << x; }
void __print(long double x) { cerr << x; }
void __print(char x) { cerr << '\'' << x << '\''; }
void __print(const char *x) { cerr << '\"' << x << '\"'; }
void __print(const string &x) { cerr << '\"' << x << '\"'; }
void __print(bool x) { cerr << (x ? "true" : "false"); }
template <typename T, typename V>
void __print(const pair<T, V> &x) {
  cerr << '{';
  __print(x.first);
  cerr << ',';
  __print(x.second);
  cerr << '}';
}
template <typename T>
void __print(const T &x) {
  int f = 0;
  cerr << '{';
  for (auto &i : x) cerr << (f++ ? ", " : ""), __print(i);
  cerr << "}";
}
void _print() { cerr << "]\n\n"; }
template <typename T, typename... V>
void _print(T t, V... v) {
  __print(t);
  if (sizeof...(v)) cerr << ", ";
  _print(v...);
}
const long long mod = 1e9 + 7;
void solve() {
  long long n, q;
  cin >> n >> q;
  string s;
  cin >> s;
  map<char, tuple<long long, long long, long long>> mp;
  while (q--) {
    char d, t;
    cin >> t >> d;
    auto it = mp[t];
    if (d == 'L') {
      get<0>(it)--;
      get<1>(it) = min(get<0>(it), get<1>(it));
    } else {
      get<0>(it)++;
      get<2>(it) = max(get<0>(it), get<2>(it));
    }
    mp[t] = it;
  }
  long long ans = 0;
  for (long long i = 0; i < n; ++i) {
    auto it = mp[s[i]];
    if (i + get<1>(it) >= 0 && get<2>(it) + i < n) {
      ;
      ans++;
    }
  }
  cout << ans;
}
int32_t main() {
  auto start = chrono::high_resolution_clock::now();
  ios::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  fio();
  long long t;
  t = 1;
  while (t--) solve();
  auto end = chrono::high_resolution_clock::now();
  TIME(start, end);
  return 0;
}
