# -*- coding: utf-8 -*-
import sys
import copy
import collections
from bisect import bisect_left
	
def main():
	N, Q = map(int, input().split())
	S = "_" + input() + "_"
	
	TD = []
	for _ in range(Q):
		tmp = input().split(" ")
		t = tmp[0]
		d = tmp[1]
		TD.append((t, d))
		
	TD.reverse()
	gake_L = 0
	gake_R = N - 1 + 2
	
	for i, val in enumerate(TD):
		t, d = val
		
		if d == "R":
			if t == S[gake_R-1]:
				gake_R -= 1
			if t == S[gake_L]:
				gake_L -= 1
		
		if d == "L":
			if t == S[gake_R]:
				gake_R += 1
			if t == S[gake_L+1]:
				gake_L += 1
	
	print(max(0, gake_R-gake_L-1))
	
	
if __name__ == "__main__":
	main()
