N,M=map(int,input().split())
result=0
mod=998244353
for x in range(1,M+1):
  if x==M:
    result+=pow(M,N,mod)*N
    result%=mod
    continue
  p=M*pow(x,-1,mod)
  p%=mod
  w=pow(x,N,mod)
  w*=1-pow(p,N,mod)
  w%=mod
  w*=pow(1-p,-1,mod)
  w%=mod
  result+=w
  result%=mod
print(result)