#include <bits/stdc++.h>
using namespace std;
inline int toInt(string s) {
  int v;
  istringstream sin(s);
  sin >> v;
  return v;
}
inline long long toLongLong(string s) {
  long long v;
  istringstream sin(s);
  sin >> v;
  return v;
}
template <class T>
inline string toString(T x) {
  ostringstream sout;
  sout << x;
  return sout.str();
}
inline vector<char> toVC(string s) {
  vector<char> data(s.begin(), s.end());
  return data;
}
template <typename List>
void SPRIT(const std::string &s, const std::string &delim, List &result) {
  result.clear();
  string::size_type pos = 0;
  while (pos != string::npos) {
    string::size_type p = s.find(delim, pos);
    if (p == string::npos) {
      result.push_back(s.substr(pos));
      break;
    } else {
      result.push_back(s.substr(pos, p - pos));
    }
    pos = p + delim.size();
  }
}
vector<string> SPRIT(const std::string &s, const std::string &delim) {
  vector<string> result;
  string::size_type pos = 0;
  while (pos != string::npos) {
    string::size_type p = s.find(delim, pos);
    if (p == string::npos) {
      result.push_back(s.substr(pos));
      break;
    } else {
      result.push_back(s.substr(pos, p - pos));
    }
    pos = p + delim.size();
  }
  return result;
}
string TRIM(const string &str, const char *trimCharacterList = " \t\v\r\n") {
  string result;
  string::size_type left = str.find_first_not_of(trimCharacterList);
  if (left != string::npos) {
    string::size_type right = str.find_last_not_of(trimCharacterList);
    result = str.substr(left, right - left + 1);
  }
  return result;
}
string REPLACE_STRING(const string source, const string find,
                      const string alt) {
  string result = source;
  string::size_type pos = 0;
  while (pos = result.find(find, pos), pos != string::npos) {
    result.replace(pos, find.length(), alt);
    pos += alt.length();
  }
  return result;
}
template <typename T>
bool VECTOR_EXISTS(vector<T> vec, T data) {
  auto itr = std::find(vec.begin(), vec.end(), data);
  size_t index = distance(vec.begin(), itr);
  if (index != vec.size())
    return true;
  else
    return false;
}
template <typename T>
void VECTOR_REMOVE_VALUE_ALL(vector<T> &vec, T data) {
  vec.erase(remove(vec.begin(), vec.end(), data), vec.end());
}
template <typename T>
vector<T> VECTOR_REMOVE_VALUE_ALL_FAST(vector<T> vec, T data) {
  vector<T> vec2;
  for (auto &x : vec)
    if (x != data) vec2.push_back(x);
  return vec2;
}
bool REG_MATCH(string const &text, regex const &re) {
  bool result = regex_match(text, re);
  return result;
}
bool REG_MATCH(string const &text, smatch &match, regex const &re) {
  bool result = regex_match(text, match, re);
  return result;
}
smatch REG_SEARCH(string const &text, regex const &re) {
  smatch m;
  regex_search(text, m, re);
  return m;
}
vector<smatch> REG_ALL_SEARCH(string const &text, regex const &re) {
  vector<smatch> matchs;
  sregex_iterator iter(text.cbegin(), text.cend(), re);
  sregex_iterator end;
  for (; iter != end; iter++) matchs.push_back(*iter);
  return matchs;
}
string REG_REPLACE(string const &text, regex const &re, string const &replace) {
  string result =
      regex_replace(text, re, replace, regex_constants::format_first_only);
  return result;
}
string REG_ALL_REPLACE(string const &text, regex const &re,
                       string const &replace) {
  string result = regex_replace(text, re, replace);
  return result;
}
template <typename T>
vector<T> COMPRESS(vector<T> v) {
  sort(v.begin(), v.end());
  v.erase(unique(v.begin(), v.end()), v.end());
  return v;
}
template <typename T>
pair<map<T, int>, map<int, T>> MAPPING(const vector<T> v) {
  map<T, int> conv;
  map<int, T> rev;
  for (int i = 0; i < v.size(); i++) conv[v[i]] = i;
  for (int i = 0; i < v.size(); i++) rev[i] = v[i];
  return make_pair(conv, rev);
}
template <typename T, typename U, typename V, typename W>
auto operator+(const std::pair<T, U> &l, const std::pair<V, W> &r)
    -> std::pair<decltype(l.first + r.first), decltype(l.second + r.second)> {
  return {l.first + r.first, l.second + r.second};
}
template <typename T, typename U, typename V, typename W>
auto operator-(const std::pair<T, U> &l, const std::pair<V, W> &r)
    -> std::pair<decltype(l.first - r.first), decltype(l.second - r.second)> {
  return {l.first - r.first, l.second - r.second};
}
double ceil_n(double dIn, long long nLen) {
  double dOut;
  dOut = dIn * pow(10.0, nLen);
  dOut = (double)(long long)(dOut + 0.9);
  return dOut * pow(10.0, -nLen);
}
double floor_n(double dIn, long long nLen) {
  double dOut;
  dOut = dIn * pow(10.0, nLen);
  dOut = (double)(long long)(dOut);
  return dOut * pow(10.0, -nLen);
}
double round_n(double dIn, long long nLen) {
  double dOut;
  dOut = dIn * pow(10.0, nLen);
  dOut = (double)(long long)(dOut + 0.5);
  return dOut * pow(10.0, -nLen);
}
int take_a_n(long long num, int n) {
  string str = toString(num);
  return str[str.length() - n] - '0';
}
int bitcount32(int bits) {
  bits = (bits & 0x55555555) + (bits >> 1 & 0x55555555);
  bits = (bits & 0x33333333) + (bits >> 2 & 0x33333333);
  bits = (bits & 0x0f0f0f0f) + (bits >> 4 & 0x0f0f0f0f);
  bits = (bits & 0x00ff00ff) + (bits >> 8 & 0x00ff00ff);
  return (bits & 0x0000ffff) + (bits >> 16 & 0x0000ffff);
}
long long bitcount64(long long bits) {
  bits = (bits & 0x5555555555555555) + (bits >> 1 & 0x5555555555555555);
  bits = (bits & 0x3333333333333333) + (bits >> 2 & 0x3333333333333333);
  bits = (bits & 0x0f0f0f0f0f0f0f0f) + (bits >> 4 & 0x0f0f0f0f0f0f0f0f);
  bits = (bits & 0x00ff00ff00ff00ff) + (bits >> 8 & 0x00ff00ff00ff00ff);
  bits = (bits & 0x0000ffff0000ffff) + (bits >> 16 & 0x0000ffff0000ffff);
  return (bits & 0x00000000ffffffff) + (bits >> 32 & 0x00000000ffffffff);
}
template <class T1, class T2>
inline bool chmin(T1 &a, T2 b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T1, class T2>
inline bool chmax(T1 &a, T2 b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <typename T1, typename T2>
istream &operator>>(istream &in, pair<T1, T2> &p) {
  in >> p.first >> p.second;
  return in;
}
template <typename T>
istream &operator>>(istream &in, vector<T> &v) {
  for (auto &x : v) in >> x;
  return in;
}
template <typename T1, typename T2>
std::ostream &operator<<(ostream &out, const std::pair<T1, T2> &p) {
  out << "[" << p.first << ", " << p.second << "]"
      << "\n";
  return out;
}
const double EPS = 1e-10;
const double PI = acos(-1.0);
const int dx[] = {-1, 0, 1, 0};
const int dy[] = {0, 1, 0, -1};
template <typename T>
inline bool BETWEEN(const T aim, const T min, const T max) {
  if (min <= aim && aim <= max) {
    return true;
  } else {
    return false;
  }
}
template <typename T1, typename T2>
inline bool IS_OUT(const T1 toY, const T1 toX, const T2 H, const T2 W) {
  return (toY < 0 || toY >= H || toX < 0 || toX >= W);
}
template <class T>
inline T SQR(const T x) {
  return x * x;
}
template <class T1, class T2>
inline T1 POW(const T1 x, const T2 y) {
  if (!y)
    return 1;
  else if ((y & 1) == 0) {
    return SQR(POW(x, y >> 1));
  } else
    return POW(x, y ^ 1) * x;
}
template <typename T>
constexpr T ABS(T x) {
  return x < 0 ? -x : x;
}
template <class Iter>
bool next_partial_permutation(Iter first, Iter middle, Iter last) {
  reverse(middle, last);
  return next_permutation(first, last);
}
template <class Iter>
bool next_combination(Iter first1, Iter last1, Iter first2, Iter last2) {
  if ((first1 == last1) || (first2 == last2)) {
    return false;
  }
  Iter m1 = last1;
  Iter m2 = last2;
  --m2;
  while (--m1 != first1 && !(*m1 < *m2)) {
  }
  bool result = (m1 == first1) && !(*first1 < *m2);
  if (!result) {
    while (first2 != m2 && !(*m1 < *first2)) {
      ++first2;
    }
    first1 = m1;
    std::iter_swap(first1, first2);
    ++first1;
    ++first2;
  }
  if ((first1 != last1) && (first2 != last2)) {
    m1 = last1;
    m2 = first2;
    while ((m1 != first1) && (m2 != last2)) {
      std::iter_swap(--m1, m2);
      ++m2;
    }
    std::reverse(first1, m1);
    std::reverse(first1, last1);
    std::reverse(m2, last2);
    std::reverse(first2, last2);
  }
  return !result;
}
template <typename T>
constexpr bool ODD(T x) {
  return x % 2 != 0;
}
template <typename T>
constexpr bool EVEN(T x) {
  return x % 2 == 0;
}
template <class T>
inline T GCD(const T x, const T y) {
  if (x < 0) return GCD(-x, y);
  if (y < 0) return GCD(x, -y);
  return (!y) ? x : GCD(y, x % y);
}
template <class T>
inline T LCM(const T x, const T y) {
  if (x < 0) return LCM(-x, y);
  if (y < 0) return LCM(x, -y);
  return x * (y / GCD(x, y));
}
template <class T>
inline T EXTGCD(const T a, const T b, T &x, T &y) {
  if (a < 0) {
    T d = EXTGCD(-a, b, x, y);
    x = -x;
    return d;
  }
  if (b < 0) {
    T d = EXTGCD(a, -b, x, y);
    y = -y;
    return d;
  }
  if (!b) {
    x = 1;
    y = 0;
    return a;
  } else {
    T d = EXTGCD(b, a % b, x, y);
    T t = x;
    x = y;
    y = t - (a / b) * y;
    return d;
  }
}
template <class T>
inline T INV_MOD(const T a, const T m) {
  T x, y;
  EXTGCD(a, m, x, y);
  return (x + m) % m;
}
template <class T>
inline bool ISPRIME(const T x) {
  if (x <= 1) return false;
  for (T i = 2; i * i <= x; i++)
    if (x % i == 0) return false;
  return true;
}
template <class T>
vector<bool> ERATOSTHENES(const T n) {
  vector<bool> arr(n + 1, true);
  arr[0] = arr[1] = false;
  for (long long i = 2; i * i <= n; i++) {
    if (arr[i]) {
      for (long long j = i * 2LL; j <= n; j += i) {
        arr[j] = false;
      }
    }
  }
  return arr;
}
template <typename T>
vector<bool> ERATOSTHENES(const T a, const T b) {
  vector<bool> small = ERATOSTHENES(b);
  vector<bool> prime(b - a, true);
  for (long long i = 2; i * i <= b; i++) {
    if (small[i]) {
      for (long long j = max(2LL, (a + i - 1) / i) * i; j < b; j += i) {
        prime[j - a] = false;
      }
    }
  }
  return prime;
}
template <typename T>
vector<T> DIVISOR(T n) {
  vector<T> v;
  for (long long i = 1; i * i <= n; ++i) {
    if (n % i == 0) {
      v.push_back(i);
      if (i != n / i) {
        v.push_back(n / i);
      }
    }
  }
  sort(v.begin(), v.end());
  return v;
}
template <typename T>
vector<vector<T>> DIVISOR_ALL(T n) {
  vector<vector<T>> res(n + 1);
  for (long long i = 1; i <= n; i++) {
    for (long long j = i; j <= n; j += i) {
      res[j].push_back(i);
    }
  }
  return res;
}
template <typename T>
vector<pair<T, long long>> FACTORIZATION(T x) {
  vector<pair<T, long long>> ans;
  for (long long i = 2; i * i <= x; i++) {
    if (x % i == 0) {
      long long count = 0;
      while (x % i == 0) {
        count++;
        x /= i;
      }
      ans.push_back(make_pair(i, count));
    }
  }
  if (x != 1) ans.push_back(make_pair(x, 1));
  return ans;
}
long long POW_MOD(long long N, long long P, long long M) {
  long long ret = 1;
  while (P > 0) {
    if (P & 1LL) ret = (ret * N) % M;
    N = (N * N) % M;
    P >>= 1LL;
  }
  return ret;
}
template <typename T>
inline T NCR(T n, T r) {
  if (r > n - r) r = n - r;
  T ans = 1LL;
  for (long long i = 0; i < r; i++) {
    ans = ans * (n - i) / (i + 1);
  }
  return ans;
}
long long NCR_MOD(long long n, long long r, long long M) {
  if (r > n - r) return NCR_MOD(n, n - r, M);
  long long numerator = 1LL;
  long long denominator = 1LL;
  for (long long i = 0; i < r; i++) {
    numerator *= (n - i);
    numerator %= M;
    denominator *= (i + 1);
    denominator %= M;
  }
  return numerator * POW_MOD(denominator, M - 2, M) % M;
}
int main() {
  int N, Q;
  cin >> N >> Q;
  string S;
  cin >> S;
  vector<char> t(Q), d(Q);
  for (int i = 0; i < Q; i++) cin >> t[i] >> d[i];
  reverse((t).begin(), (t).end());
  reverse((d).begin(), (d).end());
  int l_pos = -1;
  int r_pos = N;
  bool get_left = false;
  bool get_right = false;
  int left_sum = 0;
  int right_sum = 0;
  for (int i = 0; i < Q; i++) {
    if (r_pos >= 0) {
      if (d[i] == 'R') {
        if (r_pos >= 1 && S[r_pos - 1] == t[i]) {
          right_sum++;
          r_pos--;
          get_right = true;
        }
      }
      if (d[i] == 'L') {
        if (r_pos < N && r_pos >= 0) {
          if (S[r_pos] == t[i]) {
            get_right = false;
          }
        }
      }
    }
    if (l_pos < N) {
      if (d[i] == 'L') {
        if (l_pos < N - 1 && S[l_pos + 1] == t[i]) {
          left_sum++;
          l_pos++;
          get_left = true;
        }
      }
      if (d[i] == 'R') {
        if (l_pos < N && l_pos >= 0) {
          if (S[l_pos] == t[i]) {
            get_left = false;
          }
        }
      }
    }
    if (r_pos <= l_pos) {
      cout << 0;
      return 0;
    }
  }
  if (!get_left) {
    l_pos = -1;
  }
  if (!get_right) {
    r_pos = N;
  }
  if (r_pos > l_pos) {
    cout << r_pos - l_pos - 1 << endl;
  } else {
    cout << 0 << endl;
  }
  return 0;
}
