n,m = map(int,input().split()) 
mod = 998244353 

ans = 0 
inv_m = pow(m,mod-2,mod)

for i in range(1,m):
    r = i*inv_m % mod 
    ans += r*(1-pow(r,n,mod))*pow(1-r,mod-2,mod) % mod 
    ans %= mod 
ans += n

print(pow(m,n,mod)*ans%mod)