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

inv2 = pow(2, MOD - 2, MOD)
pows = [1] * (5 * 10 ** 5 + 10)

for i in range(5 * 10 ** 5 + 10):
    pows[i] = pow(i, n, MOD)

def sum_max(k):
    ans = k  # 最大
    r = pows[k] * (k + 1) * inv2 * n
    l = pows[k - 1] * k * inv2 * n
    ans *= r - l
    return ans % MOD

def sum_min(k):
    ans = k  # 最小
    r = pows[m - k + 1] * (k + m) * inv2 * n
    l = pows[m - k] * (k + m + 1) * inv2 * n
    ans *= r - l
    return ans % MOD

ans = 0
for k in range(1, m + 1):
    ans += sum_max(k)
    ans -= sum_min(k)
    ans %= MOD
print(ans)


"""
import itertools
tmp = 0
for ptn in itertools.product([i + 1 for i in range(m)], repeat=n):
    tmp += sum(ptn) * max(ptn)
    tmp %= MOD
print(tmp)"""