#include <bits/stdc++.h>
#define X first
#define Y second
#define INF 1000 * 1000 * 1000
#define PB push_back
const int MAX = 505;
using namespace std;
const int mod = 1000 * 1000 * 1000 + 7;

string s;
int n , q;
pair<char , char> p[200005];
int nah(int pos)
{
	for(int i = 0; i < q; i++)
	{
		if(p[i].X == s[pos])
			pos = pos + (p[i].Y == 'L' ?  -1 : 1);
		if(pos == -1)
			return -1;
		if(pos == n)
			return 1;
	}
	return 0;
}
int main()
{
	//init();
    ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
	
	cin >> n >> q >> s;
	for(int i = 0; i < q; i++)
	{
		cin >> p[i].X >> p[i].Y;
	}
	int l = -1;
	
	int r = n;
	for(int i = 17; i >= 0; i--)
	{
		if(l + (1 << i) < n && nah(l + (1 << i)) == -1)
		{
			l += (1 << i);
		}
		if(r - (1 << i) >= 0 && nah(r - (1 << i)) == 1)
		{
			r -= (1 << i);
		}
		
	}
	cout << r - l - 1 << endl;
    return 0;
}
