class Combination:

    def __init__(self, MX, MOD):
        self.MX = MX
        self.MOD = MOD

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

    def inverse(self, n):
        return self.inv[n]

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


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

cmb = Combination(max(N, M) + 1, MOD)

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

for k in range(1, min(N + 1, M) + 1):
    ans_k = cmb.combination(N, k - 1) * cmb.combination(M, k) % MOD
    ans_k = ans_k * pow(k, k - 2, MOD) * cmb.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)