#include <vector>
#include <iostream>
#include <cmath>
#include <map>
#include <unordered_map>
#include <algorithm>
#include <fstream>
#include <unistd.h>
#include <string.h>
#include <string>
#include <numeric>
#include <queue>
#include <deque>
#include <sstream>
#include <iomanip>
#include <set>
#include <stack>
#include <cassert>
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<vvl> vvvl;
typedef vector<vi> vvi;
typedef vector<vvi> vvvi;
typedef vector<bool> vb;
typedef vector<vector<bool>> vvb;
typedef vector<vvb> vvvb;
typedef vector<vvvb> vvvvb;
typedef vector<string> vs;
typedef vector<vs> vvs;
typedef vector<vvs> vvvs;
typedef vector<char> vc;
typedef vector<vector<char>> vvc;
typedef vector<double> vd;
typedef vector<vd> vvd;
typedef vector<vvd> vvvd;
typedef pair<ll, ll> PL;
typedef vector<PL> vpl;
typedef vector<vector<PL>> vvpl;
const int INF = 1001001001;
const ll LINF = 1e17;
const double pi = 3.1415926535897932;
const string endstr = "\n";
#define FOR(i, a, b) for(ll i = (a); i < b; i++)
#define RFOR(i, a, b) for(ll i = (a); i > b; i--)
#define rep(i, n) for(ll i = 0; i < n; i++)
#define rrep(i, n) for(ll i = n-1; i > -1; i--)
#define FORMAP(it, m) for(auto it = m.begin(); it != m.end(); it++)
#define ff first
#define ss second
#define pb push_back
#define epb emplace_back
#define ALL(X) (X).begin(),(X).end()

template <typename T>
T gcd(T a, T b) {
    return (a == 0) ? b : gcd(b%a, a);
}
template <typename T>
T lcm(T a, T b) {
    return a / gcd(a, b) * b;
}

bool p_comp_fs(const PL p1, const PL p2){ return p1.first < p2.first;};
bool p_comp_fg(const PL p1, const PL p2){ return p1.first > p2.first;};
bool p_comp_ss(const PL p1, const PL p2){ return p1.second < p2.second;};
bool p_comp_sg(const PL p1, const PL p2){ return p1.second > p2.second;};
template <typename T>
vector<T> uniquen(vector<T> vec){
    vec.erase(unique(vec.begin(), vec.end()), vec.end());
    return vec;
}

inline ll popcnt(ll x){return __builtin_popcountll((unsigned long long)x);};
template<class T> bool chmax(T &a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> bool chmin(T &a, T b) { if (a > b) { a = b; return true; } return false; }

string S;
ll N, Q;
vector<pair<char, char>> td;

bool okl(ll x){
    rep(i, Q){
        if(x < 0) return true;
        if(x > N-1) return false;
        if(td[i].ff == S[x]){
            if(td[i].ss == 'L') x--;
            else x++;
        }
    }
    if(x < 0) return true;
    return false;
}

bool okr(ll x){
    rep(i, Q){
        if(x > N-1) return true;
        if(x < 0) return false;
        if(td[i].ff == S[x]){
            if(td[i].ss == 'L') x--;
            else x++;
        }
    }
    if(x > N-1) return true;
    return false;
}

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cin >> N >> Q;
    cin >> S;
    rep(_, Q){
        char t, q; cin >> t >> q; td.pb({t,q});
    }
    
    
    ll ok = -1, ng = N;
    while(abs(ok-ng) > 1){
        ll mid = (ok+ng)/2;
        if(okl(mid)) ok = mid;
        else ng = mid;
    }
    ll LRem = ok+1;
    
    ok = N; ng = -1;
    while(abs(ok-ng) > 1){
        ll mid = (ok+ng)/2;
        if(okr(mid)) ok = mid;
        else ng = mid;
    }
    ll RRem = N-1-ok+1;
    cout << max(N - (LRem+RRem), 0ll) << endstr;
    return 0;
}


Measured memory_bytes: 1100