mod = 998244353
N, M = map(int, input().split())
S = input()

a_count = [0] * N
i_count = [0] * N
question_count = [0] * N
question_all = 0

for _ in range(M):
    A, B = map(int, input().split())
    A -= 1
    B -= 1
    if S[A] == "a":
        a_count[B] += 1
    elif S[A] == "i":
        i_count[B] += 1
    elif S[A] == "?":
        question_count[B] += 1
    if S[B] == "a":
        a_count[A] += 1
    elif S[B] == "i":
        i_count[A] += 1
    elif S[B] == "?":
        question_count[A] += 1

question_all = S.count("?")
inv_26 = pow(26, -1, mod)
inv_26_2 = pow(26, -2, mod)
ans = 0
for i in range(N):
    if S[i] == "o" or S[i] == "?":
        pattern = a_count[i] * i_count[i] % mod
        pattern += a_count[i] * question_count[i] * inv_26 % mod
        pattern += i_count[i] * question_count[i] * inv_26 % mod
        pattern += (question_count[i] * (question_count[i] - 1) * inv_26_2) % mod
        if S[i] == "?":
            pattern = pattern * inv_26 % mod
        ans += pattern

print(ans * pow(26, question_all, mod) % mod)