MOD = 998244353

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

max_n = M + 1
fact = [1] * (max_n + 1)
for i in range(1, max_n + 1):
    fact[i] = fact[i-1] * i % MOD

inv_fact = [1] * (max_n + 1)
inv_fact[max_n] = pow(fact[max_n], MOD-2, MOD)
for i in range(max_n-1, -1, -1):
    inv_fact[i] = inv_fact[i+1] * (i+1) % MOD

def comb(n, k):
    if k < 0 or k > n:
        return 0
    return fact[n] * inv_fact[k] % MOD * inv_fact[n - k] % MOD

# Compute initial term
pow_2n = pow(2, N, MOD)
initial = pow(M, N + 1, MOD) * (pow_2n - 1) % MOD

# Compute sum over i=1 to M
sum_part = 0
pow_MN = pow(M, N, MOD)
for i in range(1, M + 1):
    x = 2 * M - i
    pow_x = pow(x, N, MOD)
    term = (pow_x - pow_MN) % MOD
    c = comb(M + 1, i + 1)
    sign = -1 if i % 2 else 1
    contrib = term * sign * c
    contrib %= MOD
    sum_part = (sum_part + contrib) % MOD

total = (initial + sum_part) % MOD
print(total)