#define _USE_MATH_DEFINES
#include<iostream>
#include<string>
#include<queue>
#include<cmath>
#include<map>
#include<set>
#include<list>
#include<iomanip>
#include<vector>
#include<random>
#include<functional>
#include<algorithm>
#include<stack>
#include<cstdio>
#include<bitset>
#include<unordered_map>
#include<climits>
#include<fstream>
using namespace std;
///////////////////library zone!!!!!!!!!!!!!!!!!!!!!!!!!!!!
typedef long long ll;
typedef long double ld;
#define all(a) (a).begin(),(a).end()
#define EPS (1e-5)
const ll Mod = 1000000007;
const ll mod = 998244353;
struct H {
	ll x, y;
	bool operator<(const H &b) const {
		if (x != b.x) return x < b.x;
		return y < b.y;
	}
	bool operator>(const H &b) const {
		if (x != b.x) return x > b.x;
		return y > b.y;
	}
	bool operator==(const H &b) const { return x == b.x&&y == b.y; }
	bool operator!=(const H &b) const { return (*this) != b; }
};
struct P {
	ll pos, cost;
	bool operator<(const P &b) const { return cost < b.cost; }
	bool operator>(const P &b) const { return cost > b.cost; }
};
struct B {
	ll to, cost;
};
struct E {
ll from, to, cost;
bool operator<(const E &b) const { return cost < b.cost; }
bool operator>(const E &b) const { return cost > b.cost; }
};
template<typename T, typename U>
void chmin(T &a, U b) {
	if (a > b) a = b;
}
template<typename T, typename U>
void chmax(T &a, U b) {
	if (a < b) a = b;
}
template<typename T>
T max_0(T a) {
	if (a < 0) return 0;
	return a;
}
template<typename T>
T min_0(T a) {
	if (a > 0) return 0;
	return a;
}
ll read() {
	ll u;
	ll k = scanf("%lld", &u);
	return u;
}
ll gcd(ll i, ll j) {
	if (i > j) swap(i, j);
	if (i == 0) return j;
	return gcd(j%i, i);
}
ll mod_pow(ll x, ll n, ll p) {
	ll res = 1;
	while (n > 0) {
		if (n & 1) res = res * x % p;
		x = x * x % p;
		n >>= 1;
	}
	return res;
}//x^n%p
vector<string>split(string s, char c = ' ') {
	vector<string>vec;
	string h = "";
	for (int i = 0; i < s.size();) {
		int j = i;
		while (j < s.size() && s[j] != ' ') {
			h += s[j++];
		}
		if (h.size() > 0) vec.push_back(h);
		h = "";
		i = j + 1;
	}
	return vec;
}
template<typename T>
void print_vec(vector<T>a) {
	for (int i = 0; i < a.size(); i++) {
		cout << (i == 0 ? "" : " ") << a[i];
	}
	cout << endl;
}
const ll Inf = 3023372036854775807;
const int inf = 1500000000;
#define int long long
//----------------------------------------------------
int n, q;
string s;
char a[300000], b[300000];
signed main() {
	cin >> n >> q >> s;
	int l = 0, r = n, t;
	for (int i = 0; i < q; i++) {
		cin >> a[i] >> b[i];
	}
	while (r - l > 1) {
		t = (l + r) / 2;
		int k = t;
		//今k番地にいる。
		for (int i = 0; i < q; i++) {
			if (a[i] == s[k]) {
				if (b[i] == 'L') {
					k--;
					if (k == 0) {
						l = t;
						goto loop;
					}
				}
				else {
					if (k == n - 1) break;
					k++;
				}
			}
		}
		r = t;
	loop:;
	}
	t = l;
	for (int i = 0; i < q; i++) {
		if (a[i] == s[t]) {
			if (b[i] == 'L') {
				if (t == 0) goto rrt;
				t--;
			}
			else {
				if (t == n - 1) {
					break;
				}
				t++;
			}
		}
	}
	l--;
rrt:;
	int ans = l + 1;
	l = -1, r = n - 1;
	while (r - l > 1) {
		t = (l + r) / 2;
		int k = t;
		for (int i = 0; i < q; i++) {
			if (a[i] == s[k]) {
				if (b[i] == 'L') {
					if (k == 0) break;
					k--;
				}
				else {
					if (k == n - 1) {
						r = t;
						goto kick;
					}
					k++;
				}
			}
		}
		l = t;
	kick:;
	}
	t = r;
	for (int i = 0; i < q; i++) {
		if (a[i] == s[t]) {
			if (b[i] == 'L') {
				if (t == 0) break;
				t--;
			}
			else {
				if (t == n - 1) {
					goto rrr;
				}
				t++;
			}
		}
	}
	r++;
rrr:;
	cout << n - (ans + (n - r)) << endl;
}

Measured memory_bytes: 1028