#include <bits/stdc++.h>

std::vector<char> t, d;
std::string s;
int N, Q;

int end(int);

int main()
{
	scanf("%d%d", &N, &Q);
	
	std::cin >> s;

	t.resize(Q);
	d.resize(Q);
	for (int i{}; i < Q; i++) scanf(" %c %c", &t[i], &d[i]);
	int left{-1}, right{N};
	while (left + 1 < right)
	{
		int mid{(left + right) / 2};
		if (end(mid) == -1) left = mid;
		else right = mid;
	}
	int sum{left + 1};
	left = -1; right = N;
	while (left + 1 < right)
	{
		int mid{(left + right) / 2};
		if (end(mid) == N) right = mid;
		else left = mid;
	}
	sum += N - right;
	printf("%d\n", N - sum);

	return 0;
}

int end(int pos)
{
	for (int i{}; i < Q; i++)
	{
		if (pos < 0 || pos >= N) return pos;
		if (t[i] != s[pos]) continue;
		if (d[i] == 'R') pos++;
		else pos--;
	}
	return pos;
}