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

S = input()
G = [[] for _ in range(N)]
for _ in range(M):
    a, b = map(int, input().split())
    a -= 1
    b -= 1
    G[a].append(b)
    G[b].append(a)

mod = 998244353
q = S.count("?")
mypow = [1]
for _ in range(q):
    mypow.append(mypow[-1] * 26 % mod)

ans = 0
for i in range(N):
    if S[i] != "o" and S[i] != "?": continue
    pp = q - (S[i] == "?")
    ac = 0
    ic = 0
    xc = 0
    for j in G[i]:
        if S[j] == "a":
            ac += 1
        elif S[j] == "i":
            ic += 1
        elif S[j] == "?":
            xc += 1
    ans += ac * ic * mypow[pp] % mod
    if xc > 0:
        ans += ac * xc * mypow[pp-1] % mod
        ans += xc * ic * mypow[pp-1] % mod
    if xc > 1:
        ans += xc * (xc-1) * mypow[pp-2] % mod
    ans %= mod

print(ans)