n,m=map(int,input().split())
s=input()
ab=[[*map(int,input().split())]for _ in range(m)]
M=998244353
g=[[]for _ in range(n)]
for a,b in ab:
  g[a-1]+=b-1,
  g[b-1]+=a-1,
hs=s.count('?')
ans=0
for p in range(n):
  a=i=h=0
  for v in g[p]:
    a+=s[v]=='a'
    i+=s[v]=='i'
    h+=s[v]=='?'
  p0=pow(26,hs,M)
  p1=pow(26,hs-1,M)if hs else 0
  p2=pow(26,hs-2,M)if hs>1 else 0
  p3=pow(26,hs-3,M)if hs>2 else 0
  if s[p]=='o':
    ans+=a*i*p0+(h>0)*(a*p1+i*p1)+(h>1)*p2*2
  if s[p]=='?':
    ans+=a*i*p1+(h>0)*(a*p2+i*p2)+(h>1)*p3*2
  ans%=M
print(ans)