n, q = map(int, input().split())
s = input()
t = [None] * q
d = [None] * q
for i in range(q):
    t[i], d[i] = input().split()
l, r = 0, n + 1
while r - l > 1:
    m = (l + r) // 2
    c = m - 1
    for i in range(q):
        if s[c] == t[i]:
            if d[i] == 'L':
                c -= 1
            else:
                c += 1
        if c < 0:
            l = m
            break
    else:
        r = m
a = l
l, r = 0, n + 1
while r - l > 1:
    m = (l + r) // 2
    c = m - 1
    for i in range(q):
        if s[c] == t[i]:
            if d[i] == 'L':
                c -= 1
            else:
                c += 1
        if c >= n:
            r = m
            break
    else:
        l = m
b = n - l
print(max(0, n - a - b))
