#include <bits/stdc++.h>
using namespace std;

#define NDEBUG
#include <cassert>


typedef long long ll;
typedef long double Double;
typedef unsigned long long ull;
typedef pair<int, int> ii;
typedef pair<ll, ll> llll;
typedef pair<double, double> dd;

typedef vector<int> vi;
typedef vector<vector<int>> vvi;
typedef vector<ii> vii;
typedef vector<vector<ii>> vvii;
typedef vector<ll> vll;
typedef vector<vector<ll>> vvll;
typedef vector<llll> vllll;
typedef vector<bool> vb;
typedef vector<string> vs;
typedef vector<double> vd;
typedef vector<long double> vD;

#define sz(a) int((a).size())
#define pb push_back
#define eb emplace_back
#define FOR(var, from, to) for (int var = (from); var <= (to); ++var)
#define rep(var, n) for (int var = 0; var < (n); ++var)
#define rep1(var, n) for (int var = 1; var <= (n); ++var)
#define repC2(vari, varj, n)               \
  for (int vari = 0; vari < (n)-1; ++vari) \
    for (int varj = vari + 1; varj < (n); ++varj)
#define repC3(vari, varj, vark, n)                  \
  for (int vari = 0; vari < (n)-2; ++vari)          \
    for (int varj = vari + 1; varj < (n)-1; ++varj) \
      for (int vark = varj + 1; vark < (n); ++vark)
#define ALL(c) (c).begin(), (c).end()
#define RALL(c) (c).rbegin(), (c).rend()
#define tr(i, c) for (auto i = (c).begin(); i != (c).end(); ++i)
#define found(s, e) ((s).find(e) != (s).end())
#define mset(arr, val) memset(arr, val, sizeof(arr))
#define mid(x, y) ((x) + ((y) - (x)) / 2)
#define IN(x, a, b) ((a) <= (x) && (x) <= (b))
#define cons make_pair
#define clamp(v, lo, hi) min(max(v, lo), hi)
#define ABS(x) max((x), -(x))
#define PQ(T) priority_queue<T, vector<T>, greater<T>>

template <typename T1, typename T2>
inline void amin(T1& a, T2 const& b) {
  if (a > b) a = b;
}
template <typename T1, typename T2>
inline void amax(T1& a, T2 const& b) {
  if (a < b) a = b;
}
template <typename X, typename T>
auto vectors(X x, T a) {
  return vector<T>(x, a);
}
template <typename X, typename Y, typename Z, typename... Zs>
auto vectors(X x, Y y, Z z, Zs... zs) {
  auto cont = vectors(y, z, zs...);
  return vector<decltype(cont)>(x, cont);
}

inline ll square(ll x) { return x * x; }
inline ll gcd(ll a, ll b) {
  while (a) swap(a, b %= a);
  return b;
}
inline ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }
template <typename T>
inline T mod(T a, T b) {
  return ((a % b) + b) % b;
}

template <typename T>
int find_left(vector<T>& v, T elem) {
  return (int)(upper_bound(v.begin(), v.end(), elem) - v.begin()) - 1;
}
template <typename T>
int find_right(vector<T>& v, T elem) {
  return (int)(lower_bound(v.begin(), v.end(), elem) - v.begin());
}

int solve(int N, int Q, char* s, vector<char>& t, vector<char>& d) {
  assert(strlen(s) >= N);
  s[N] = 0;
  auto f = [&](int ix) -> int {
    assert(IN(ix, 0, N - 1));
    rep(i, Q) {
      if (ix == -1 || ix == N) break;
      char letter = s[ix];
      if (letter == t[i]) {
        if (d[i] == 'L')
          --ix;
        else
          ++ix;
      }
    }
    return ix;
  };

  int fL = f(0), fR = f(N - 1);

  if (fL == N) return 0;
  if (fR == -1) return 0;

  if (fL == -1 && fR == N) {
    int leftmost, rightmost;
    {
      int lo = 0, hi = N - 1;
      while (lo + 1 < hi) {
        int x = (lo + hi) / 2;
        int fx = f(x);
        if (0 <= fx) {
          hi = x;
        } else {
          lo = x;
        }
      }
      leftmost = hi;
    }
    {
      int lo = 0, hi = N - 1;
      while (lo + 1 < hi) {
        int x = (lo + hi) / 2;
        int fx = f(x);
        if (fx <= N - 1) {
          lo = x;
        } else {
          hi = x;
        }
      }
      rightmost = lo;
    }
    if (leftmost <= rightmost) {
      return rightmost - leftmost + 1;
    } else {
      return 0;
    }
  }
  if (fL == -1) {
    assert(IN(fR, 0, N - 1));
    int ng = 0, ok = N - 1;
    while (ng + 1 < ok) {
      int x = (ng + ok) / 2;
      int fx = f(x);
      if (IN(fx, 0, N - 1)) {
        ok = x;
      } else {
        ng = x;
      }
    }
    int leftmost = ok, rightmost = fR;
    return rightmost - leftmost + 1;
  }
  if (fR == N) {
    assert(IN(fL, 0, N - 1));
    int ok = 0, ng = N - 1;
    while (ok + 1 < ng) {
      int x = (ok + ng) / 2;
      int fx = f(x);
      if (IN(fx, 0, N - 1)) {
        ok = x;
      } else {
        ng = x;
      }
    }
    int leftmost = fL, rightmost = ok;
    return rightmost - leftmost + 1;
  }

  return N;
}

int main() {
  int N, Q;
  scanf("%d %d%*c", &N, &Q);
  char s[N + 3];
  fgets(s, N + 3, stdin);
  vector<char> t(Q), d(Q);
  rep(i, Q) { scanf("%c %c%*c", &t[i], &d[i]); }
  printf("%d\n", solve(N, Q, s, t, d));
  return 0;
}


Measured memory_bytes: 4060