#include<bits/stdc++.h>
using namespace std;
#define fs first
#define sc second
#define mp make_pair
#define pb push_back
#define eb emplace_back
#define ALL(A) A.begin(),A.end()
#define RALL(A) A.rbegin(),A.rend()
typedef long long LL;
typedef pair<char,char> P;
const LL mod=1000000007;
const LL LINF=1LL<<62;
const LL INF=1<<17;



int main(){
    int n,q;cin >> n >> q;
    string s;
    cin >> s;
    vector<P> v;
    for (int i = 0; i < q; i++) {
        char x,y;cin >> x >> y;
        v.pb({x,y});
    }
    int k=0,z=0;
    int l=0,r=n-1;
    for (int i = q-1; i >=0; i--) {
        if(v[i].sc=='L'){
            if(v[i].fs==s[l]) l++;
            if(v[i].fs==s[min(n-1,r+1)]) r=min(r+1,n-1);
        }
        else{
            if(v[i].fs==s[r]) r--;
            if(v[i].fs==s[max(0,l-1)]) l=max(0,l-1);
        }
    }
    cout << n-(l+(n-1-r)) << endl;
    return 0;
}
