#include <bits/stdc++.h>
using namespace std;
inline bool isvowel(char c) {
  c = tolower(c);
  if (c == 'a' || c == 'e' || c == 'i' || c == 'y' || c == 'o' || c == 'u')
    return 1;
  return 0;
}
const double eps = 0.000001;
const long double pi = acos(-1);
const int maxn = 1e7 + 9;
const int mod = 1e9 + 7;
const long long MOD = 1e18 + 9;
const long long INF = 1e18 + 123;
const int inf = 2e9 + 11;
const int mxn = 1e6 + 9;
const int N = 6e5 + 123;
const int M = 22;
const int pri = 997;
const int Magic = 2101;
const int dx[] = {-1, 0, 1, 0};
const int dy[] = {0, -1, 0, 1};
int n, m, k;
vector<int> g[31];
string s;
int add[31];
int main() {
  cin >> n >> m;
  cin >> s;
  s = '#' + s;
  for (int i = 1; i <= n; i++) {
    g[s[i] - 'A'].push_back(i);
  }
  for (int i = 1; i <= m; i++) {
    char c, d;
    cin >> c >> d;
    int t = c - 'A';
    if (g[t].empty()) continue;
    vector<int> nw;
    for (auto id : g[t]) {
      int nxt = id;
      if (d == 'L')
        nxt--;
      else
        nxt++;
      nw.push_back(nxt);
    }
    g[t].clear();
    for (auto nxt : nw) {
      if (nxt >= 1 && nxt <= n) g[s[nxt] - 'A'].push_back(nxt);
    }
  }
  int ans = 0;
  for (int i = 0; i < 30; i++) {
    ans += g[i].size();
  }
  cout << ans;
  return 0;
}
