#include "bits/stdc++.h"
using namespace std;
#define Rep(i,n) for(int i=0;i<(int)(n);i++)
#define For(i,n1,n2) for(int i=(int)(n1);i<(int)(n2);i++)
#define REP(i,n) for(ll i=0;i<(ll)(n);i++)
#define RREP(i,n) for(ll i=((ll)(n)-1);i>=0;i--)
#define FOR(i,n1,n2) for(ll i=(ll)(n1);i<(ll)(n2);i++)
#define RFOR(i,n1,n2) for(ll i=((ll)(n1)-1);i>=(ll)(n2);i--)
#define all(a)  (a).begin(),(a).end()
#define SORT(a) sort((a).begin(),(a).end())
#define oorret 0
#define oor(x) [&](){try{x;} catch(const out_of_range& oor){return oorret;} return x;}()
#define IOS cin.tie(0),ios::sync_with_stdio(false)
typedef long long ll;
typedef unsigned long long ull;
typedef pair<ll, ll> P;
template<typename T1, typename T2> inline bool chmin(T1& a, T2 b) { if (a > b) { a = b; return 1; }return 0; }
template<typename T1, typename T2> inline bool chmax(T1& a, T2 b) { if (a < b) { a = b; return 1; }return 0; }
template<class Type>struct is_vector : std::false_type {};
template<class ValueType, class Alloc>struct is_vector<std::vector<ValueType, Alloc>> : std::true_type {};
template <typename T> inline ostream& operator << (ostream& out, const vector<T>& v) {
    if (v.empty())return out;
    constexpr bool is_vector_v = is_vector<T>::value;
    if (is_vector_v)for (auto itr = v.begin(); itr != v.end();)out << (*itr), out << ((++itr != v.end()) ? "\n" : "");
    else for (auto itr = v.begin(); itr != v.end();)out << (*itr), out << ((++itr != v.end()) ? " " : "");
    return out;
}
inline void put() {}
template<class T> inline void put(const T& first) { std::cout << first<<"\n"; }
template<class T, class... N> inline void put(const T& first, const N& ... rest) { std::cout << first << " "; put(rest...); }
inline void putn() {}
template<class T, class... N> inline void putn(const T& first, const N& ... rest) { std::cout << first << "\n"; putn(rest...); }

int n,q;
string s;
vector<char> t,d;

bool able1(int m){
    int x = m;
    if(x<0){
        return false;
    }
    REP(i,q){
        if(t[i]==s[x]){
            if(d[i]=='L'){
                x--;
            }else{
                x++;
            }
            if(x<0){
                return false;
            }else if(x>=n){
                return true;
            }
        }
    }
    return true;
}

bool able2(int m){
    int x = m;
    if(x>=n){
        return false;
    }
    REP(i,q){
        if(t[i]==s[x]){
            if(d[i]=='L'){
                x--;
            }else{
                x++;
            }
            if(x>=n){
                return false;
            }else if(x<0){
                return true;
            }
        }
    }
    return true;
}

int main(){
    IOS;
    cin >> n >> q;
    cin >> s;
    t.resize(q);
    d.resize(q);
    REP(i,q){
        cin >> t[i] >> d[i];
    }
    int res1,res2;
    int lb,ub;
    lb=-2;
    ub=n+2;
    while(ub-lb>1){
        int mid = (lb+ub)/2;
        if(able1(mid)){
            ub = mid;
        }else{
            lb = mid;
        }
    }
    res1=ub;
    lb=-2;
    ub=n+2;
    while(ub-lb>1){
        int mid = (lb+ub)/2;
        if(able2(mid)){
            lb = mid;
        }else{
            ub = mid;
        }
    }
    res2=ub;
    put(res2-res1);
    return 0;
}



Measured memory_bytes: 976