from collections import defaultdict
import sys
input = sys.stdin.readline

N, Q = map(int, input().split())
s = input()
q = []
for _ in range(Q):
  q.append(input().split())
q.reverse()

l = 0
r = N-1
for i in range(Q):
  t, d = q[i]
  if l-1 >= 0 and t == s[l-1] and d == 'R':
    l -= 1
  elif t == s[l] and d == 'L':
    l += 1

  if r+1 <= N-1 and t == s[r+1] and d == 'L':
    r += 1
  elif t == s[r] and d == 'R':
    r -= 1

print(max(0, r-l+1))