n, m = map(int, input().split())
mod = 998244353
S = input()
node = [[] for _ in range(n)]
for _ in range(m):
    a, b = [int(x)-1 for x in input().split()]
    node[a].append(b)
    node[b].append(a)


dp = [[[0, 0, 0, 0] for _ in range(3)] for _ in range(n)]
for i in range(n):
    if S[i] == "a":
        dp[i][0][0] = 1
    elif S[i] == "?":
        dp[i][0][1] = 1
    else:
        continue
    for nxt in node[i]:
        if S[nxt] == "o":
            for j in range(4):
                dp[nxt][1][j] += dp[i][0][j]
        elif S[nxt] == "?":
            for j in range(1, 4):
                dp[nxt][1][j] += dp[i][0][j-1]

for now in range(n):
    for nxt in node[now]:
        if S[now] not in "o?":
            continue
        if S[nxt] == "i":
            for j in range(4):
                dp[nxt][2][j] += dp[now][1][j]; dp[nxt][2][j] %= mod
        elif S[nxt] == "?":
            for j in range(1, 4):
                dp[nxt][2][j] += dp[now][1][j-1]; dp[nxt][2][j] %= mod
        if S[nxt] == "?" and S[now] == "o":
            dp[nxt][2][2] -= 1
        elif S[nxt] == "?" and S[now] == "?":
            dp[nxt][2][3] -= 1

ans = 0
cnt = S.count("?")
D = [pow(26, cnt-i, mod) for i in range(4)]

for i in range(n):
    for j in range(4):
        ncnt = cnt - j
        ans += dp[i][2][j] * D[j] % mod; ans %= mod

print(ans)