# encoding:utf-8
import copy
import numpy as np
import random
import bisect #bisect_left　これで二部探索の大小検索が行える

N,Q = map(int, input().split())
s = input()
td = [input().split() for i in range(Q)]

td.reverse()

nl = 0
nr = N-1
L = []
R = []
for i in td:#全ての指示
    # print(L,R)
    if i[1]=="L":
        if nl < N:
            if s[nl] == i[0]:
                L.append(i[0])
                nl += 1
            if len(R) != 0:
                if R[-1]==i[0]:
                    R.pop()
    else:
        if nr >= 0:
          if s[nr] == i[0]:
            R.append(i[0])
            nr -= 1
        if len(L) != 0:
          if L[-1] == i[0]:
            L.pop()
            nl -= 1

print(N-len(L)-len(R))
