#include<iostream>
#include<vector>
#include<algorithm>
#include<string>

using namespace std;

typedef long long int ll;
const int INF = 1<<30;
const long long LINF = 1LL<<60;

int main(){
    int n, q;
    string s;
    cin >> n >> q >> s;
    vector<pair<char, char>> t(q);
    for(int i = 0; i < q; i++){
        char a, b;
        cin >> a >> b;
        t[i] = make_pair(a, b);
    }
    int l = 0, r = n - 1;
    for(int i = q - 1; i >= 0; i--){
        if(l < n && t[i].first == s[l] && t[i].second == 'L'){
            l++;
        }else if(l > 0 && t[i].first == s[l - 1] && t[i].second == 'R'){
            l--;
        }
        if(r >= 0 && t[i].first == s[r] && t[i].second == 'R'){
            r--;
        }else if(r < n - 1 && t[i].first == s[r + 1] && t[i].second == 'L'){
            r++;
        }
        if(r < l) break;
    }
    cout << max(0, n - l - (n - 1 - r)) << endl;
    return 0;
}
