import sys
I=sys.stdin.readlines()
N,Q=map(int,I[0].split())
S=I[1][:-1]
query=[]
for i in range(Q):
  query.append(list(I[i+2].split()))
  if query[i][1]=='L':
    query[i][1]=-1
  else:
    query[i][1]=1
L,R,M,X=0,N+1,0,0
while R>L:
  M=(L+R+1)//2
  if M==0:
    R=M
    break
  if M==N+1:
    L=M
    break
  X=M-1
  for i in range(Q):
    if query[i][0]==S[X]:
      X+=query[i][1]
    if X==-1 or X==N:
      break
  if X==-1:
    L=M
  else:
    R=min(M,R-1)
P=[1]*(N+2)
for i in range(R+1):
  P[i]=0
L,R=0,N+1
while R>L:
  M=(L+R)//2
  if M==0:
    R=M
    break
  if M==N+1:
    L=M
    break
  X=M-1
  for i in range(Q):
    if query[i][0]==S[X]:
      X+=query[i][1]
    if X==-1 or X==N:
      break
  if X==N:
    R=M
  else:
    L=max(L+1,M)
for i in range(R,N+2):
  P[i]=0
print(sum(P))