#include<iostream>
using namespace std;
char t[200000],d[200000];
int n,q;
string s;

int simulate(int x){
	for(int i=0;i<q;i++){
		if(s[x]==t[i]){
			if(d[i]=='L') x--;
			else x++;
			if(x<0 || n<=x) break;
		}
	}
	return x;
}

int main(){
	cin >> n >> q;
	cin >> s;
	for(int i=0;i<q;i++) cin >> t[i] >> d[i];

	int left=-1,right=n;
	while(left+1<right){
		int mid=(left+right)/2;
		int p=simulate(mid);
		if(p==-1) left=mid;
		else right=mid;
	}
	int l=left;
	left=-1,right=n;
	while(left+1<right){
		int mid=(left+right)/2;
		int p=simulate(mid);
		if(p==n) right=mid;
		else left=mid;
	}
	int r=right;
	cout << n-((l+1)+(n-r)) << endl;
	return 0;
}
