#include<bits/stdc++.h>
using namespace std;

#define F first
#define S second
#define PB push_back
#define all(x) x.begin(), x.end()

typedef long long ll; 
typedef long double ld;

const int N = 1000 * 100 + 10, M = 210; 
const int mod = 1000 * 1000 * 1000 + 7;

string s;
string t, x;
int n, q;

int get(int i)
{
	for(int j = 0; j < q; j++)
	{
		if(s[i] != t[j]) continue;
		if(x[j] == 'L') i--;
		else i++;
		if(i < 0) return 1;
		if(i == n) return 2;
	}
	return 0;
}

int32_t main()
{
	ios::sync_with_stdio(0); cin.tie(0);
	cin>> n >> q;
	cin>> s;
	for(int i = 0; i < q; i++)
	{
		char z, y;
		cin>> z >> y;
		t += z;
		x += y;
	}
	int l = -1, r = n;
	while(r - l > 1)
	{
		int mid = (l + r) / 2;
		if(get(mid) == 1) l = mid;
		else r = mid;
	}
	int lo = -1, hi = n;
	while(hi - lo > 1)
	{
		int mid = (hi + lo) / 2;
		if(get(mid) == 2) hi = mid;
		else lo = mid;
	}
	cout<< n - ((l + 1) + (n - hi)) << endl;
}
