n, q = map(int,input().split())
s = "_" + input() + "_"
l, r = 0, n+1

for (t,d) in [input().split() for i in range(q)][::-1]:
  L = d == 'L'
  R = d == 'R'
  l += (t==s[l+1] and L) - (t==s[l] and R)
  r += (t==s[r] and L) - (t==s[r-1] and R)
print(r-l-1)
