#include <bits/stdc++.h>

#define FOR(i,a,b) for(int i= (a); i<((int)b); ++i)
#define RFOR(i,a) for(int i=(a); i >= 0; --i)
#define FOE(i,a) for(auto i : a)
#define ALL(c) (c).begin(), (c).end()
#define RALL(c) (c).rbegin(), (c).rend()
#define DUMP(x)  cerr << #x << " = " << (x) << endl;
#define SUM(x) std::accumulate(ALL(x), 0LL)
#define MIN(v) *std::min_element(v.begin(), v.end())
#define MAX(v) *std::max_element(v.begin(), v.end())
#define EXIST(v,x) (std::find(v.begin(), v.end(), x) != v.end())
#define BIT_ON(bit, i) (((bit >> i) & 1) > 0)

typedef long long LL;
template<typename T> std::vector<T> make_v(size_t a){return std::vector<T>(a);}
template<typename T,typename... Ts> auto make_v(size_t a, Ts... ts){ return std::vector<decltype(make_v<T>(ts...))>(a,make_v<T>(ts...));}    // C++14
template<typename T,typename V> typename std::enable_if<std::is_class<T>::value==0>::type fill_v(T &t,const V &v){t=v;}
template<typename T,typename V> typename std::enable_if<std::is_class<T>::value!=0>::type fill_v(T &t,const V &v){for(auto &e:t) fill_v(e,v);}
template<class T> inline T ceil(T a, T b) { return (a + b - 1) / b; }
template<class T> inline void print(T x) { std::cout << x << std::endl; }
template<class T> inline void print_vec(const std::vector<T> &v) { for (int i = 0; i < v.size(); ++i) {  if (i != 0) {std::cout << " ";} std::cout << v[i];} std::cout << "\n"; }
template<class T> inline bool inside(T y, T x, T H, T W) {return 0 <= y and y < H and 0 <= x and x < W; }
template<class T> inline double euclidean_distance(T y1, T x1, T y2, T x2) { return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2)); }
template<class T> inline double manhattan_distance(T y1, T x1, T y2, T x2) { return abs(x1 - x2) + abs(y1 - y2); }
template<typename T> T &chmin(T &a, const T &b) { return a = std::min(a, b); }
template<typename T> T &chmax(T &a, const T &b) { return a = std::max(a, b); }

template<class T> inline std::vector<T> unique(std::vector<T> v) {
    sort(v.begin(), v.end());
    v.erase(unique(v.begin(), v.end()), v.end());
    return v;
}
// 初項s, 交差dのn個の数列の和
long long sum_of_arithmetic_progression(long long s, long long d, long long n) {
    return n * (2 * s + (n - 1) * d) / 2;
}

const int INF = 1 << 30;
const double EPS = 1e-9;
const long double PI = acos(-1.0);
const std::vector<int> dy4 = {0, -1, 0, 1}, dx4 = {1, 0, -1, 0};
const std::vector<int> dy8 = { 0, -1, 0, 1, 1, -1, -1, 1 }, dx8 = { 1, 0, -1, 0, 1, 1, -1, -1 };


using namespace std;


bool can_remain(int now, const string &S, const vector<pair<char, int>> &ope) {
    int N = S.size();

    FOE(p, ope) {
        if (p.first == S[now]) {
            now += p.second;
        }

        if (now < 0 or now >= N) {
            return false;
        }
    }

    return true;
}

// 開区間(low, high)で条件を満たす一番左
int binary_search_left(long long low, long long high, const string &S, const vector<pair<char, int>> &ope) {
    // (low, high)
    while (high - low > 1) {
        long long middle = (low + high) / 2;
        if (can_remain(middle, S, ope)) {
            high = middle;
        }
        else {
            low = middle;
        }
    }

    return high;
}

// 開区間(low, high)で条件を満たす一番右
int binary_search_right(long long low, long long high, const string &S, const vector<pair<char, int>> &ope) {
    // (low, high)
    while (high - low > 1) {
        long long middle = (low + high) / 2;
        if (can_remain(middle, S, ope)) {
            low = middle;
        }
        else {
            high = middle;
        }
    }

    return low;
}

// 開区間(low, high)で条件を満たすindex
// なければ-1
int find(long long low, long long high, const string &S, const vector<pair<char, int>> &ope) {
    auto l = binary_search_left(low, high, S, ope);
    if (l != S.size()) {
        return l;
    }
    auto r = binary_search_left(low, high, S, ope);
    if (r != -1) {
        return r;
    }

    return -1;
}


int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);

    int N, Q;
    cin >> N >> Q;
    string S;
    cin >> S;

    auto ope = make_v<pair<char, int>>(Q);
    FOR(i, 0, Q) {
        char T, D;
        cin >> T >> D;
        if (D == 'L') {
            ope[i] = make_pair(T, -1);
        }
        else {
            ope[i] = make_pair(T, +1);
        }
    }

    int idx = find(-1, S.size(), S, ope);
    if (idx == -1) {
        print(N);
        return 0;
    }

    auto l = binary_search_left(-1, idx + 1, S, ope);
    auto r = binary_search_right(idx - 1, S.size(), S, ope);
    if (l <= r) {
        auto ans = r - l + 1;
        print(ans);
    }
    else {
        print(0);
    }

    return 0;
}



Measured memory_bytes: 2196