def is_left_removed(i, S, td):
  direction = {'L': -1, 'R': +1}
  for t, d in td:
    if S[i] == t:
      i += direction[d]
    if i < 0:
      return True
    if i >= N:
      return False
  return False
def is_right_removed(i, S, td):
  direction = {'L': -1, 'R': +1}
  for t, d in td:
    if S[i] == t:
      i += direction[d]
    if i >= N:
      return True
    if i < 0:
      return False
  return False

N, Q = map(int, raw_input().split())
s = raw_input()
td = [raw_input().split() for _ in range(Q)]

# left
l = 0
r = N - 1
l_res = -1
while (l <= r):
  target = (r + l) / 2
  if is_left_removed(target, s, td):
    l = target + 1
    l_res = target
  else:
    r = target - 1

# right
l = 0
r = N - 1
r_res = N
while (l <= r):
  target = (r + l) / 2
  if is_right_removed(target, s, td):
    r = target - 1
    r_res = target
  else:
    l = target + 1

print N - min(N, l_res + 1 + N - r_res)