N,M=map(int, input().split())
S=input()
D=[[0]*4 for i in range(N)]
for _ in range(M):
  a,b=map(int, input().split())
  a-=1;b-=1
  SS='aoi?'
  for i in range(4):
    if S[b]==SS[i]:
      D[a][i]+=1
  for i in range(4):
    if S[a]==SS[i]:
      D[b][i]+=1

e=S.count('?') 
mod=998244353 
ans=0
for i in range(N):
  a,b,c,d=D[i]
  if S[i]=='o':
    ans+=a*c*pow(26,e,mod)
    ans%=mod
    ans+=d*c*pow(26,e-1,mod)
    ans%=mod
    ans+=a*d*pow(26,e-1,mod)
    ans%=mod
    ans+=d*(d-1)*pow(26,e-2,mod)
    ans%=mod
  if S[i]=='?':
    ans+=a*c*pow(26,e-1,mod)
    ans%=mod
    ans+=d*c*pow(26,e-2,mod)
    ans%=mod
    ans+=a*d*pow(26,e-2,mod)
    ans%=mod
    ans+=d*(d-1)*pow(26,e-3,mod)
    ans%=mod
print(ans)