MX = 10 ** 6
MOD = 998244353

fact = [1] * (MX + 1)
inv = [1] * (MX + 1)
fact_inv = [1] * (MX + 1)
for i in range(2, MX + 1):
    fact[i] = (fact[i - 1] * i) % MOD
    inv[i]  = ((- inv[MOD % (i)]) * (MOD // i)) % MOD
    fact_inv[i] = (fact_inv[i - 1] * inv[i]) % MOD
    
def factorial(n):
    return fact[n]

def inverse(n):
    return inv[n]

def combination(n, r):
    return (fact[n] * fact_inv[n - r] * fact_inv[r]) % MOD


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

ans = pow(M, 2 * N + 1, MOD)

for k in range(1, min(N + 1, M) + 1):
    ans_k = combination(N, k - 1) * combination(M, k) % MOD
    ans_k = ans_k * pow(k, max(0, k - 2), MOD) * factorial(k - 1) * pow(2, k - 1, MOD) % MOD
    ans_k = ans_k * pow(M - k, 2 * (N - k + 1), MOD) % MOD
    ans = (ans - ans_k) % MOD

print(ans)