#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define ALL(v) (v).begin(), (v).end()

int N, Q;
string s;
vector<char> t, d;

int sim(int x) {
  for (int i = 0; i < Q; ++i) {
    if (s[x] == t[i]) {
      if (d[i] == 'L') x--;
      else x++;
    }

    // マス１から落ちるとき
    if (x < 0) return -1;

    // マスNから落ちるとき
    else if (x > N-1) return -2;
  }

  return 0;
}

int main()
{
  cin >> N >> Q;
  cin >> s;
  t.resize(Q), d.resize(Q);

  for (int i = 0; i < Q; ++i) cin >> t[i] >> d[i];

  int le=-1, ri=N, mid;
  while (ri-le>1) {
    mid = (le+ri)/2;
    if (sim(mid) == -1) le = mid;
    else ri = mid;
  }

  int lle=-1, rri=N;
  while (rri-lle>1) {
    mid = (lle+rri)/2;
    if (sim(mid) == -2) rri = mid;
    else lle = mid;
  }

  cout << lle - ri + 1 << endl;
}