def int_raw():
    return int(raw_input())

def ss_raw():
    return raw_input().split()

def ints_raw():
    return map(int, ss_raw())

INF = 1 << 29

N,Q  = ints_raw()
S = raw_input()
td =[]
for i in xrange(Q):
    td.append(ss_raw())
td = map(lambda b:(b[0],-1 if b[1]=="L" else 1),td)


def is_die_l(n):
    pos = n
    if pos < 0:
        return True
    for i in xrange(Q):
        if pos > N-1:
            return False
        if td[i][0]==S[pos]:
            pos+=td[i][1]
        if pos < 0:
            return True
    return False

def is_die_r(n):
    pos = n
    if pos > N-1:
        return True
    for i in xrange(Q):
        if pos < 0:
            return False
        if td[i][0]==S[pos]:
            pos+=td[i][1]
        if pos > N-1:
            return True
    return False

def ans():
    mostLeft = -1
    mostRight = N
    
    high = N-1
    if is_die_l(high):
        return 0
    while  (high-mostLeft)>1:
        mid = (mostLeft + high)/2
        if is_die_l(mid):
            mostLeft = mid
        else:
            high = mid
    mostLeft = high

    low =0 
    if is_die_r(low):
        return 0
    while  (mostRight-low)>1:
        mid = (mostRight + low)/2
        if is_die_r(mid):
            mostRight = mid
        else:
            low = mid
    mostRight = low
    
    return mostRight-mostLeft+1


print ans()
