import numpy as np
N, Q = map(int, input().split())
s=input()
goreme= np.array([1]*N)
dic={}
pre_ans=0
for i,moji in enumerate(s):#文字index関係整理
    dic.setdefault(moji,[])
    dic[moji].append(i)
for k in range(Q):
    jumon=input()
    if jumon[0] in dic.keys():
        move= np.array([0]*N)
        if jumon[-1]=='R':
            for index in dic[jumon[0]]:
                if goreme[index]!=0:
                    if index==N-1:
                        move[index]-=goreme[index]
                        pre_ans+=goreme[index]
                    else:
                        move[index]-=goreme[index]
                        move[index+1]+=goreme[index]
        else:
            for index in dic[jumon[0]]:
                if goreme[index]!=0:
                    if index==0:
                        move[index]-=goreme[index]
                        pre_ans+=goreme[index]
                    else:
                        move[index]-=goreme[index]
                        move[index-1]+=goreme[index]     
        goreme+=move
        #print(goreme)
print(N-pre_ans)
    