#include <bits/stdc++.h>
#include <random>

using namespace std;

typedef unsigned long long ull;
typedef long long ll;
typedef long double ld;
//#define int ll
//#define int __int128
//#define ll __int128
//typedef __int128 long long;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector< vi > vvi;
typedef vector< vvi > vvvi;
typedef vector<short> vs;
typedef vector<vs> vvs;
typedef vector<vvs> vvvs;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<vvl> vvvl;
typedef vector<ld> vld;
typedef vector<vld> vvld;
typedef vector<vvld> vvvld;
typedef vector<string> vst;
typedef vector<vst> vvst;
typedef pair<ld, ld> pld;
typedef complex<double> base;

#define inmin(a, b) a = min(a, (b))
#define inmax(a, b) a = max(a, (b))
#define ALL(a) a.begin(),a.end()
#define RALL(a) a.rbegin(),a.rend()
#define sqr(x) ((x) * (x))
#define fori(i, n) for(int i = 0; i < int(n); ++i)
#define SZ(a) ((int)((a).size()))
#define triple(T) tuple<T, T, T>
#define quad(T) tuple<T, T, T, T>
#define watch(x) cerr << (#x) << " = " << (x) << endl;

#ifdef MAX_HOME
#define cerr cout
#else
#define cerr if (false) cerr
#endif

const double PI = 2 * acos(0.0);
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
mt19937_64 rng_64(chrono::steady_clock::now().time_since_epoch().count());

const string DIGITS = "0123456789";
const string ALPH = "abcdefghijklmnopqrstuvwxyz";

template <class T0, class T1>
inline ostream & operator << (ostream &out, pair<T0, T1> &a) {
    return out << "{" << a.first << ", " << a.second << "}";
}

template <class T0, class T1, class T2>
inline ostream & operator << (ostream &out, tuple<T0, T1, T2> &a) {
    return out << "{" << get<0>(a) << ", " << get<1>(a) << ", " << get<2>(a) << "}";
}

template <class T0, class T1, class T2, class T3>
inline ostream & operator << (ostream &out, tuple<T0, T1, T2, T3> &a) {
    return out << "{" << get<0>(a) << ", " << get<1>(a) << ", " << get<2>(a) << ", " <<  get<3>(a) << "}";
}

template<class T>
inline ostream & operator << (ostream &out, vector<T> &a) {
    out << "[";
    fori (i, a.size())
        out << a[i] << vector<string>{", ", "]  "}[i + 1 == a.size()];
    return out;
}



void smain();

signed main() {
    ios::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);

#ifdef MAX_HOME
    freopen("input.txt", "r", stdin);
    clock_t start = clock();
#endif
    cout << setprecision(12) << fixed;
    smain();
#ifdef MAX_HOME
    cout << "\n\n\n\nTOTAL EXECUTION TIME: " << float( clock () - start ) /  CLOCKS_PER_SEC << endl;
#endif
}

const int N = 2e5 + 100;
const int L = 26;

vi a;
int n;
vector<pii> queries;

bool check_pref(int ind) {
    for (auto q : queries) {
        ind += q.first == a[ind] ? q.second : 0;
        if (ind == n) return false;
        if (ind < 0) return true;
    }
    return false;
}

bool check_suf(int ind) {
    for (auto q : queries) {
        ind += q.first == a[ind] ? q.second : 0;
        if (ind == n) return true;
        if (ind < 0) return false;
    }
    return false;
}

void smain() {

    int  q;
    cin >> n >> q;
    string s;
    a.resize(n);
    cin >> s;
    fori (i, n) a[i] = s[i] - 'A';
    fori (i, q) {
        string f, s;
        cin >> f >> s;
        queries.push_back({f[0] - 'A', s[0] == 'R' ? +1 : -1});
    }

    int l = -1, r = n;
    while (r - l > 1) {
        int mid = r + l >> 1;
        (check_pref(mid) ? l : r) = mid;
    }
    int L = l;

    l = -1, r = n;
    while (r - l > 1) {
        int mid = r + l >> 1;
        (check_suf(mid) ? r : l) = mid;
    }
    int R = r;
    int ans = L + 1 + n - R;
    cout << n - ans;
}

Measured memory_bytes: 4492