#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 7;
int n, q;
char c[N];
char a[N], b[N];
int dl, dr;
int die(int x) {
  for (int i = 1; i <= q; i++) {
    if (a[i] != c[x]) continue;
    if (b[i] == 'R')
      x++;
    else
      x--;
    if (x == 0) return -1;
    if (x == n + 1) return 1;
  }
  return 0;
}
int main() {
  cin >> n >> q;
  for (int i = 1; i <= n; i++) cin >> c[i];
  for (int i = 1; i <= q; i++) cin >> a[i] >> b[i];
  int l = 0, r = n + 1, md;
  while (r - l > 1) {
    md = (r + l) / 2;
    if (die(md) == -1)
      l = md;
    else
      r = md;
  }
  dl = l;
  l = 0, r = n + 1, md;
  while (r - l > 1) {
    md = (r + l) / 2;
    if (die(md) == 1)
      r = md;
    else
      l = md;
  }
  dr = r;
  if (dr <= dl) dr = dl + 1;
  cout << n - dl - (n - (dr) + 1);
  return 0;
}
