import sys
input = sys.stdin.readline

N,Q=map(int,input().split())
S=input().strip()
M=[input().split() for i in range(Q)]

PLACE=-1

for i in range(Q-1,-1,-1):

    if PLACE+1<N and M[i][0]==S[PLACE+1] and M[i][1]=="L":
        PLACE+=1

    elif PLACE>=0 and M[i][0]==S[PLACE] and M[i][1]=="R":
        PLACE-=1

    if PLACE==N:
        print(0)
        sys.exit()

PLACE2=N

for i in range(Q-1,-1,-1):

    if PLACE2-1>=0 and M[i][0]==S[PLACE2-1] and M[i][1]=="R":
        PLACE2-=1

    elif PLACE2<=N-1 and M[i][0]==S[PLACE2] and M[i][1]=="L":
        PLACE2+=1

    if PLACE==-1:
        print(0)
        sys.exit()

print(max(0,N-(PLACE+1+(N-PLACE2))))
    