#include<bits/stdc++.h>
//using namespace std;
#pragma GCC target("avx")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#define rep(i,j,n) for(ll i=(ll)(j);i<(ll)(n);i++)
#define REP(i,j,n) for(ll i=(ll)(j);i<=(ll)(n);i++)
#define per(i,j,n) for(ll i=(ll)(j);(ll)(n)<=i;i--)
#define ll long long
#define ALL(a) (a).begin(),(a).end()
#define disup(A,key) distance(A.begin(),upper_bound(ALL(A),(ll)(key)))
#define dislow(A,key) distance(A.begin(),lower_bound(ALL(A),(ll)(key)))
#define pb emplace_back
#define mp std::make_pair
#define endl "\n"
using std::cin;
using std::cout;
using std::vector;
using std::string;
using std::upper_bound;
using std::lower_bound;
using vi=vector<ll>;
using vii=vector<vi>;
using pii=std::pair<ll,ll>;
constexpr ll MOD=1e9+7;
//constexpr ll MOD=998244353;
//constexpr ll MOD=100000;
constexpr ll MAX=1e7;
constexpr ll INF=(1ll<<60);
template<class T>
class prique :public std::priority_queue<T, std::vector<T>, std::greater<T>> {};
struct Binary_indexed_tree{
    int N;
    vi bit;
    Binary_indexed_tree(int n):N(n){
        bit.resize(N+1,0);
    }
    void add(int x,int a){
        for(x;x<=N;x+=(x&-x)) bit[x]+=a;
    }
    ll sum(int x){
        ll ret=0;
        for(x;x>0;x-=(x&-x)) ret+=bit[x];
        return ret;
    }
    ll lower_bound(ll X){
        if(sum(N)<X) return -1;
        ll ret=0,memo=1,sum=0;
        while(memo*2<=N) memo*=2;
        while(memo>0){
            if(memo+ret<=N&&sum+bit[memo+ret]<X){
                sum+=bit[memo+ret];
                ret+=memo;
            }
            memo/=2;
        }
        return ret+1;
    }
};
struct Union_Find{
    ll N;
    vi par;
    vi siz;
    Union_Find(int n):N(n){
        par.resize(N);
        siz.resize(N,1);
        rep(i,0,N) par[i]=i;
    }
    ll root(ll X){
        if(par[X]==X) return X;
        return par[X]=root(par[X]);
    }
    bool same(ll X,ll Y){
        return root(X)==root(Y);
    }
    void unite(ll X,ll Y){
        X=root(X);
        Y=root(Y);
        if(X==Y) return;
        par[X]=Y;
        siz[Y]+=siz[X];
        siz[X]=0;
    }
    ll size(ll X){
        return siz[root(X)];
    }
};
ll modpow(ll X,ll Y,ll mod){
    ll sum=X,cnt=1;
    vi A;
    while(cnt<=Y){
        A.pb(sum);
        sum*=sum;
        sum%=mod;
        cnt*=2;
    }
    int M=A.size();
    ll ret=1;
    REP(i,1,M){
        if(Y>=(1ll<<M-i)){
            Y-=(1ll<<M-i);
            ret*=A[M-i];
            ret%=mod;
        }
    }
    return ret;
}
ll fac[MAX],finv[MAX],inv[MAX];
void COMinit() {
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for (int i = 2; i < MAX; i++){
        fac[i] = fac[i - 1] * i % MOD;
        inv[i] = MOD - inv[MOD%i] * (MOD / i) % MOD;
        finv[i] = finv[i - 1] * inv[i] % MOD;
    }
}
ll COM(ll n,ll r){
    if(n<r||n<0||r<0) return 0;
    return fac[n]*finv[r]%MOD*finv[n-r]%MOD;
}
signed main(){
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    ll N,Q; cin>>N>>Q;
    string S; cin>>S;
    vector<char> T(Q),D(Q);
    rep(i,0,Q){
        cin>>T[i]>>D[i];
    }
    ll left=0,right=N;
    ll ans=N;
    while(left+1<right){
        ll mid=(left+right)/2;
        if(mid==0) left=mid;
        else{
            ll X=mid-1;
            bool flag=1;
            rep(i,0,Q){
                if(S[X]==T[i]){
                    if(D[i]=='L') X--;
                    else X++;
                }
                if(X==-1){
                    flag=0;
                    break;
                }
                if(X==N) break;
            }
            if(flag) right=mid;
            else left=mid;
        }
    }
    ll memo=left;
    ll x=right-1;
    bool f=1;
    rep(i,0,Q){
        if(S[x]==T[i]){
            if(D[i]=='L') x--;
            else x++;
        }
        if(x==-1){
            f=0;
            break;
        }
        if(x==N) break;
    }
    if(!f) memo=right;
    ans-=memo;
    left=0,right=N;
    while(left+1<right){
        ll mid=(left+right)/2;
        if(mid==0) left=mid;
        else{
            ll X=N-mid;
            bool flag=1;
            rep(i,0,Q){
                if(S[X]==T[i]){
                    if(D[i]=='L') X--;
                    else X++;
                }
                if(X==N){
                    flag=0;
                    break;
                }
                if(X==-1) break;
            }
            if(flag) right=mid;
            else left=mid;
        }
    }
    memo=left;
    x=N-right,f=1;
    rep(i,0,Q){
        if(S[x]==T[i]){
            if(D[i]=='L') x--;
            else x++;
        }
        if(x==N){
            f=0;
            break;
        }
        if(x==-1) break;
    }
    if(!f) memo=right;
    ans-=memo;
    cout<<ans<<endl;
}

Measured memory_bytes: 976