/*
 * 	If you gave me a chance
 * 		I'll take it
 * 			It's a shot in the dark
 * 				But I will make it:D
 */
#pragma GCC optimize("Ofast")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#include <bits/stdc++.h>
using namespace std;
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
#ifndef rd
#define endl '\n'
#endif
#ifdef rd
#define trace(...) cout<<"Line:"<<__LINE__<<" "; __f(#__VA_ARGS__, __VA_ARGS__)
template<typename Arg1>
void __f(const char* name, Arg1&& arg1) {
	cout<<name<<" : "<<arg1<<endl;
}
template<typename Arg1, typename ... Args>
void __f(const char* names, Arg1&& arg1, Args&&... args) {
	const char* comma=strchr(names+1,',');
	cout.write(names,comma-names)<<" : "<<arg1<<" | ";
	__f(comma+1,args...);
}
#else
#define trace(...)
#endif
#define deb cout<<"Line: "<<__LINE__<<" plz "
#define pb push_back
#define fi first
#define se second
#define int long long
typedef long long ll;
typedef long double f80;
#define double long double
#define pii pair<int,int>
#define pll pair<ll,ll>
#define sz(x) ((long long)x.size())
#define fr(a,b,c) for(int a=b; a<=c; a++)
#define rep(a,b,c) for(int a=b; a<c; a++)
#define trav(a,x) for(auto &a:x)
#define all(con) con.begin(),con.end()
const ll infl=2e18;
const int infi=2e9;
const int mod=1e9+7;
typedef vector<int> vi;
typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> oset;
mt19937 rang(chrono::high_resolution_clock::now().time_since_epoch().count());
auto clk=clock();
int rng(int lim) {
	uniform_int_distribution<int> uid(0,lim-1);
	return uid(rang);
}

void solve() {
	int n,q;
	cin>>n>>q;
	string s;
	cin>>s;
	int lo=-1,hi=n-1,mid=(lo+hi+1)/2;
	char te1,te2;
	vector<pair<char,char>> moves;
	for(int i=0; i<q; i++) {
		cin>>te1>>te2;
		moves.pb({te1,te2});
	}
//	trace(s);
	while(lo<hi) {
//		trace(lo,hi);
		int place=mid;
		bool dark=0;
		for(int i=0; i<q; i++) {
			if(s[place]==moves[i].fi) {
				if(moves[i].se=='L')
					place--;
				else
					place++;
				if(place==n) {
					break;
				}
				if(place==-1) {
					dark=1;
					break;
				}
			}
		}
		if(dark) {
			lo=mid;
		} else {
			hi=mid-1;
		}
		mid=(lo+hi+1)/2;
	}
	int ans=mid+1;
	lo=0;
	hi=n;
	mid=(lo+hi)/2;
	while(lo<hi) {
//		trace(lo,hi);
		int place=mid;
		bool dark=0;
		for(int i=0; i<q; i++) {
			if(moves[i].fi==s[place]) {
				if(moves[i].se=='R')
					place++;
				else
					place--;
				if(place==-1) {
					break;
				}
				if(place==n) {
					dark=1;
					break;
				}
			}
		}
		if(dark)
			hi=mid;
		else
			lo=mid+1;
		mid=(lo+hi)/2;
	}
	ans+=n-mid;
	cout<<n-ans<<endl;
}
signed main() {
	ios_base::sync_with_stdio(0),cin.tie(0),cout.tie(0);
	srand(chrono::high_resolution_clock::now().time_since_epoch().count());
	int t=1;
//	cin>>t;
	while(t--)
		solve();
#ifdef rd
	cerr<<endl<<endl<<(double)(clock()-clk)/CLOCKS_PER_SEC<<endl;
#endif
	return 0;
}
