N,M = map(int,input().split())

S = input()

lis = [ [] for i in range(N) ]

for i in range(M):
    A,B = map(int,input().split())
    A -= 1
    B -= 1
    lis[A].append(B)
    lis[B].append(A)

qnum_base = 0
for i in range(N):
    if S[i] == "?":
        qnum_base += 1
    
mod = 998244353
ans = 0

for v in range(N):

    aoiq = [0,0,0,0]

    if S[v] not in "o?":
        continue

    if S[v] == "o":
        qnum = qnum_base
    else:
        qnum = qnum_base-1

    for i in lis[v]:
        if S[i] == "a":
            aoiq[0] += 1
        elif S[i] == "o":
            aoiq[1] += 1
        elif S[i] == "i":
            aoiq[2] += 1
        elif S[i] == "?":
            aoiq[3] += 1

    now = aoiq[0] * aoiq[2] * pow(26,qnum,mod) % mod

    if aoiq[3] >= 1:
        now += aoiq[0] * aoiq[3] * pow(26,qnum-1,mod) % mod
        now %= mod

        now += aoiq[3] * aoiq[2] * pow(26,qnum-1,mod) % mod
        now %= mod

    if aoiq[3] >= 2:
        now += aoiq[3] * (aoiq[3]-1) * pow(26,qnum-2,mod) % mod
        now %= mod

    ans += now

    # print (now)
    ans %= mod

print (ans % mod)