MOD = 998244353

def main():
    import sys
    N, M = map(int, sys.stdin.readline().split())
    
    if M == 0:
        print(0)
        return
    
    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
    
    part1 = pow(M, N + 1, MOD) * (pow(2, N, MOD) - 1) % MOD
    
    sum_terms = 0
    for s in range(1, M + 1):
        s_plus_1 = s + 1
        c = comb(M + 1, s_plus_1)
        base = (2 * M - s) % MOD
        pow_base = pow(base, N, MOD)
        pow_MN = pow(M, N, MOD)
        diff = (pow_base - pow_MN) % MOD
        term = c * diff % MOD
        if s % 2 == 1:
            term = (-term) % MOD
        sum_terms = (sum_terms + term) % MOD
    
    total = (part1 + sum_terms) % MOD
    print(total)

if __name__ == "__main__":
    main()