from collections import deque
N,M=map(int,input().split())
S=input()
C="aoi"
Qcnt=S.count("?")
Q=[]
for i in range(N):
    if S[i]=="a":Q.append(((i,),0))
    elif S[i]=="?":Q.append(((i,),1))
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)
Q=deque(Q)
ans=0
while Q:
    path,qcnt=Q.popleft()
    for nxt in G[path[-1]]:
        if nxt in set(path):continue
        if S[nxt]==C[len(path)]:
            if len(path)==2:
                ans+=26**(Qcnt-qcnt)
            else:Q.append((path+(nxt,),qcnt))
        elif S[nxt]=="?":
            if len(path)==2:
                ans+=26**(Qcnt-(qcnt+1))
            else:Q.append((path+(nxt,),qcnt+1))
print(ans%998244353)