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

g = []
for i in range(N):
    g.append([])

for i in range(M):
    a, b = map(int, input().split())
    a -= 1
    b -= 1
    
    g[b].append(a)
    g[a].append(b)

MOD = 998244353

power26 = []
power26.append(1)
for i in range(N):
    power26.append((power26[-1] * 26) % MOD)

q = 0
for i in range(0, N):
    if S[i] == '?':
        q += 1

ans = 0

for i in range(0, N):
    if S[i] != 'o' and S[i] != '?':
        continue
    n = g[i]
    for j in range(0, len(n)):
        for k in range(0, len(n)):
            if j == k:
                continue
            
            c = 0
            if S[n[j]] == '?':
                c += 1
            elif S[n[j]] != 'a':
                continue
            
            if S[n[k]] == '?':
                c += 1
            elif S[n[k]] != 'i':
                continue
            
            if S[i] == '?':
                c += 1
            
            ans += power26[q - c]
            ans %= MOD

print(ans)