N,M=map(int,input().split())
S=input()
edge=[[] for _ in range(N)]
for _ in range(M):
    a,b=map(int,input().split())
    edge[a-1].append(b-1)
    edge[b-1].append(a-1)
qc=S.count('?')
p=998244353
ans=0
for i in range(N):
    if S[i] == "a" or S[i] == "i":
        continue
    use = qc
    if S[i] == "?":
        use -= 1
    ac,ic,qqc=0,0,0
    for e in edge[i]:
        if S[e] == "a":
            ac+=1
        elif S[e] == "i":
            ic+=1
        elif S[e] == "?":
            qqc+=1
    #aとi
    ans+=ac*ic*pow(26,use,p)
    ans%=p
    #aと?
    ans+=ac*qqc*pow(26,use-1,p)
    ans%=p
    #iと?
    ans+=ic*qqc*pow(26,use-1,p)
    ans%=p
    #?と?
    ans+=qqc*(qqc-1)*pow(26,use-2,p)
    ans%=p
print(ans)