#include <bits/stdc++.h>

using namespace std;

#define int long long
// #define double long double
#define FOR(i, a, b) for(int i = (a); i < (b); ++i)
#define FORR(i, a, b) for(int i = (a); i > (b); --i)
#define REP(i, n) for(int i = 0; i < (n); ++i)
#define REPR(i, n) for(int i = n; i >= 0; i--)
#define FOREACH(x, a) for(auto &(x) : (a))
#define VECCIN(x)                                                              \
    for(auto &youso_ : (x)) cin >> youso_
#define bitcnt(x) __builtin_popcount(x)
#define lbit(x) __builtin_ffsll(x)
#define rbit(x) __builtin_clzll(x)
#define SZ(x) ((long long)(x).size())
#define fi first
#define se second
#define All(a) (a).begin(), (a).end()
#define rAll(a) (a).rbegin(), (a).rend()
#define cinfast() cin.tie(0), ios::sync_with_stdio(false)
#define PERM(c)                                                                \
    sort(All(c));                                                              \
    for(bool cp = true; cp; cp = next_permutation(All(c)))
#define MKORDER(n)                                                             \
    vector<int> od(n);                                                         \
    iota(All(od), 0LL);

template <typename T = long long> inline T IN() {
    T x;
    cin >> x;
    return (x);
}
inline void CIN() {}
template <class Head, class... Tail>
inline void CIN(Head &&head, Tail &&... tail) {
    cin >> head;
    CIN(move(tail)...);
}
#define CCIN(...)                                                              \
    char __VA_ARGS__;                                                          \
    CIN(__VA_ARGS__)
#define DCIN(...)                                                              \
    double __VA_ARGS__;                                                        \
    CIN(__VA_ARGS__)
#define LCIN(...)                                                              \
    long long __VA_ARGS__;                                                     \
    CIN(__VA_ARGS__)
#define SCIN(...)                                                              \
    string __VA_ARGS__;                                                        \
    CIN(__VA_ARGS__)
#define Yes(a) cout << (a ? "Yes" : "No") << "\n"
#define YES(a) cout << (a ? "YES" : "NO") << "\n"
#define Printv(v)                                                              \
    {                                                                          \
        FOREACH(x, v) { cout << x << " "; }                                    \
        cout << "\n";                                                          \
    }
template <typename T = string> inline void eputs(T s) {
    cout << s << "\n";
    exit(0);
}
template <typename A, size_t N, typename T>
void Fill(A (&array)[N], const T &val) {
    std::fill((T *)array, (T *)(array + N), val);
}

template <typename T> using PQG = priority_queue<T, vector<T>, greater<T>>;
template <typename T> using PQ = priority_queue<T>;

typedef long long ll;
typedef vector<ll> VL;
typedef vector<VL> VVL;
typedef pair<ll, ll> PL;
typedef vector<PL> VPL;
typedef vector<bool> VB;
typedef vector<double> VD;
typedef vector<string> VS;

const int INF = 1e9;
const int MOD = 1e9 + 7;
// const int MOD = 998244353;
const ll LINF = 1e18;
const double PI = atan(1.0) * 4.0;
const ll dw[] = {1, 1, 0, -1, -1, -1, 0, 1};
const ll dh[] = {0, 1, 1, 1, 0, -1, -1, -1};
#define PI 3.141592653589793238

signed main() {
    LCIN(N, Q);
    SCIN(S);
    string t, d;
    REP(i, Q) {
        SCIN(tt, dd);
        t += tt;
        d += dd;
    }
    auto check1 = [&](ll k) {
        ll idx = k - 1;
        REP(i, Q) {
            if(S[idx] == t[i]) {
                if(d[i] == 'L')
                    idx--;
                else
                    idx++;
                if(idx < 0)
                    return true;
                else if(idx > N - 1)
                    return false;
            }
        }
        return false;
    };
    auto check2 = [&](ll k) {
        ll idx = N - k;
        REP(i, Q) {
            if(S[idx] == t[i]) {
                if(d[i] == 'L')
                    idx--;
                else
                    idx++;
                if(idx < 0)
                    return false;
                else if(idx > N - 1)
                    return true;
            }
        }
        return false;
    };
    ll ans = 0;
    ll lb = 0, ub = N + 1;
    while(ub - lb > 1) {
        ll mid = (ub + lb) / 2;
        if(check1(mid))
            lb = mid;
        else
            ub = mid;
    }
    ans += lb;
    lb = 0, ub = N + 1;
    while(ub - lb > 1) {
        ll mid = (ub + lb) / 2;
        if(check2(mid))
            lb = mid;
        else
            ub = mid;
    }
    ans += lb;
    cout << N - ans << "\n";
}

Measured memory_bytes: 1024