import sys
input = sys.stdin.readline

N,M=list(map(int,input().split()))
mod=998244353

ALL=pow(M,N,mod)
ANS=ALL*N

for i in range(2,M+1):
    #print(ANS)
    k=pow(M,mod-2,mod)*(M-i+1)

    #print(k)
    ANS=(ANS+ALL*k*(1-pow(k,N,mod))*pow(1-k,mod-2,mod))%mod

print(ANS%mod)