#include <iostream>
using namespace std;

int N,Q;
char t[200010],d[200010];
string S;

bool ok(int id){
    int now = id;
    for(int i=1;i<=Q;i++){
        if(S[now]==t[i]){
            if(d[i]=='L') now--;
            else now++;
        }
        if(now==-1 || now==N) return true;
    }
    return false;
}

int main(){
    cin >> N >> Q >> S;
    for(int i=1;i<=Q;i++){
        cin >> t[i] >> d[i];
    }
    int l1 = -1,r1 = N;
    while(l1+1<r1){
        int m = (l1+r1)/2;
        if(ok(m)) l1 = m;
        else r1 = m;
    }
    int l2 = -1,r2 = N;
    while(l2+1<r2){
        int m = (l2+r2)/2;
        if(ok(m)) r2 = m;
        else l2 = m;
    }
    if(l1>=r2) cout << 0 << endl;
    else cout << N-(l1+1)-(N-r2) << endl;
}