#a,b,c = [int(i) for i in input().split()]

import sys
input = sys.stdin.readline

n,q = [int(i) for i in input().split()]
s=input()
td = [[i for i in input().split()] for _ in [0]*q]
td=td[::-1]

#print(n,q,td)

l=-1; r=n
for t,d in td:
    if d=="L":
        if l!=n-1:
            moji=s[l+1]
            if moji == t:
                l+=1
        moji=s[r]
        if moji == t:
            r+=1
            

    if d=="R":
        if r!=0:
            moji=s[r-1]
            if moji == t:
                r-=1
        moji=s[l]
        if moji == t:
            l-=1
        
    
#    print(l,r)
if l < r:
    print(n-(l+1)-(n-r))
else:
    print(0)


        