from sys import stdin,setrecursionlimit#,set_int_max_str_digits
#import pypyjit
#pypyjit.set_param('max_unroll_recursion=-1')
setrecursionlimit(20000000) # これこどふぉだと無理
#set_int_max_str_digits(200010)
mod = 998244353 
ii = lambda :int(stdin.readline())
mi = lambda :map(int,stdin.readline().split())
li = lambda :list(mi())
gmi = lambda :map(lambda x: int(x) - 1, stdin.readline().split())
gi = lambda :list(map(lambda x: 0 if x == "." else 1,input())) # グリッド入力受け取り
py = lambda :print("Yes")
pn = lambda :print("No")
pf = lambda :print("First") 
ps = lambda :print("Second")
vec = [(1,0),(-1,0),(0,-1),(0,1)]
vec1 = [(1,0),(1,1),(0,1),(-1,1),(-1,0),(-1,-1),(0,-1),(1,-1)] #8方向
inf = 10**18

from collections import defaultdict 
n,m = mi() 

s = input() 
k = s.count("?")

g = defaultdict(list) 

for _ in range(m):
    u,v = gmi() 
    g[u].append(v) 
    g[v].append(u) 

pow = [1]*(k+1) 

for i in range(k):
    pow[i+1] = pow[i]*26 
    pow[i+1] %= mod 

def check(t):
    ret = 0 
    if s[t[0]] == "?":
        ret += 1
    if s[t[1]] == "?":
        ret += 1 
    elif s[t[1]] != "o":
        return -1
    if s[t[2]] == "?":
        ret += 1 
    elif s[t[2]] != "i":
        return -1
    return ret 

ans = 0 

st = [] 

for j in range(n):
    if s[j] == "o" or s[j] == "?":
        tmp = int(s[j] == "?")
    else:continue 
    for i in g[j]:
        if s[i] == "a" or s[i] == "?":
            tmp1 = tmp + int(s[i] == "?")
        else:continue 
        for k in g[j]:
            if i == k:continue 
            if s[k] == "i" or s[k] == "?":
                t = tmp1 + int(s[k] == "?")
                ans += pow[k-t]
                ans %= mod 



print(ans)