#include <bits/stdc++.h>
using namespace std;
 
using ll = long long;
using ld = long double;
using vi = vector<int>;
using vvi = vector<vector<int>>;
using vl = vector<ll>;
using vvl = vector<vector<ll>>;
#define FOR(i, m, n) for (int i = (m); i < (n); i++)
#define FORR(i, m, n) for (int i = (m); i >= (n); i--)
#define REP(i, n) FOR(i, 0, (n))
#define REPR(i, n) FORR(i, (n) - 1, 0)
#define REP1(i, n) FOR(i, 1, (n) + 1)
#define REPS(c, s) for (char c : s)
#define ALL(c) (c).begin(), (c).end()
#define SORT(c) sort(ALL(c))
#define REV(c) reverse(ALL(c))
#define sz(v) (int)v.size()
#define endl '\n'
template<class T> inline bool chmin(T& a, T b) {if (a > b) {a = b; return true;} return false;}
template<class T> inline bool chmax(T& a, T b) {if (a < b) {a = b; return true;} return false;}
template<class T> inline void printv(vector<T>& v) {int n = sz(v); REP(i, n) cout << v[i] << (i == n - 1 ? endl : ' ');}
template<class T> inline void printvv(vector<vector<T>>& v) {for (auto u : v) printv(u);}
template<class T> inline void printlnv(vector<T>& v) {int n = sz(v); REP(i, n) cout << v[i] << endl;}
const int MOD = 1000000007;
const int INF = 1000000001;
const ll LINF = 1000000001000000001LL;
 
void solve();
 
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout << fixed << setprecision(numeric_limits<double>::max_digits10);
    solve();
    return 0;
}

template<typename D, class... A> class BinarySearch {
    D left;
    D right;
    function<bool(D, A...)> func;

    public:
        BinarySearch(D l, D r, function<bool(D, A...)> f) {
            left = l;
            right = r;
            func = f;
        }

        D calc(A... args) {
            while (abs(right - left) > 1) {
                D middle = (left + right) / 2;
                if (func(middle, args...)) {
                    left = middle;
                } else {
                    right = middle;
                }
            }
            return left;
        }
};

template<typename D, class... A> class BinarySearchR {
    D left;
    D right;
    function<bool(D, A...)> func;

    public:
        BinarySearchR(D l, D r, function<bool(D, A...)> f) {
            left = l;
            right = r;
            func = f;
        }

        D calc(A... args) {
            while (abs(right - left) > 1) {
                D middle = (left + right) / 2;
                if (func(middle, args...)) {
                    right = middle;
                } else {
                    left = middle;
                }
            }
            return right;
        }
};

void solve() {
    int n, q;
    string s;
    cin >> n >> q >> s;
    vector<char> t(q);
    vector<char> d(q);
    REP(i, q) cin >> t[i] >> d[i];
 
    auto check = [&](int m) {
        int p = m;
        REP(i, q) {
            if (s[p] == t[i]) {
                if (d[i] == 'L') p--;
                else p++;
                if (p < 0) return true;
            }
        }
        return false;
    };
 
    auto check_r = [&](int m) {
        int p = m;
        REP(i, q) {
            if (s[p] == t[i]) {
                if (d[i] == 'L') p--;
                else p++;
                if (p >= n) return true;
            }
        }
        return false;
    };
 
    BinarySearch<int> bs(-1, n, check);
    int l = bs.calc();
 
    BinarySearchR<int> bs_r(-1, n, check_r);
    int r = bs_r.calc();
    cout << n - (l + 1 + n - r) << endl;
}


Measured memory_bytes: 976