MOD = 998244353

half = pow(2, MOD - 2, MOD)

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

s = M * pow(M, N, MOD) % MOD
for i in range(M):
    s -= pow(i, N, MOD)
    s %= MOD

# print(s)

answer = N * (M + 1) % MOD * s % MOD
answer -= pow(M, N, MOD) * (M + 1) % MOD * N % MOD * (1 + M) % MOD * half % MOD
print(answer % MOD)