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

X=pow(M,N,Mod)*(M-1)
Y=0
for l in range(1,M):
    Y+=pow(l,N,Mod)

two_inv=pow(2,Mod-2,Mod)
Z=N*(M+1)*(X-2*Y)*two_inv%Mod

print(Z)