N , Q = map(int , input().split())
s = input()
tdlist = [list(input().split()) for _ in range(Q)]
#print(tdlist)
slist = [[s[j] ,1] for j in range(N)]
#print(slist)
ans = N
for td in tdlist:
    if td[1] == 'L':
        if td[0] == slist[0][0]:
            ans -= slist[0][1]
            slist[0][1] = 0
        for i in range(len(slist)-1):
            if slist[i+1][0] == td[0]:
                slist[i][1] += slist[i+1][1]
                slist[i+1][1] = 0
    if td[1] == 'R':
        if td[0] == slist[-1][0]:
            ans -= slist[-1][1]
            slist[-1][1] = 0
        for i in reversed(range(len(slist)-1)):
            if slist[i][0] == td[0]:
                slist[i+1][1] += slist[i][1]
                slist[i][1] = 0
    #print(slist)
print(ans)