N,Q = map(int, input().split())
S = input()

t = [0]*Q
d = [0]*Q
for q in range(Q):
    t[q],d[q] = map(str, input().split())


s1 = 0
sN = N-1

for q in reversed(range(Q)):
    if t[q] == S[s1] and d[q] == 'L':
        s1 += 1
    elif s1 > 0:
        if d[q] == 'R' and S[s1-1] == t[q]:
            s1 -= 1
    if t[q] == S[sN] and d[q] == 'R':
        sN -= 1
    elif sN < N-1:
        if d[q] == 'L' and S[sN+1] == t[q]:
            sN += 1
    if s1 > sN:
        break
    #print(s1,sN)


print(sN-s1+1)