def main():
	n, q = map(int, input().split())
	s = input()
	Q = [input().split() for _ in range(q)]
	l, r = -1, n
	while r - l > 1:
		c = m = (l + r) // 2
		for t, d in Q:
			if s[c] == t:
				c += 1 if d == "R" else -1
				if c == -1 or c == n:
					break
		if c == -1:
			l = m
		else:
			r = m
	a = l
	l, r = -1, n
	while r - l > 1:
		c = m = (l + r) // 2
		for t, d in Q:
			if s[c] == t:
				c += 1 if d == "R" else -1
				if c == -1 or c == n:
					break
		if c == n:
			r = m
		else:
			l = m
	b = r
	print(0 if b <= a else b - a - 1)

if __name__ == '__main__':
	main()