MOD = 998244353

def main():
    import sys
    N, M = map(int, sys.stdin.readline().split())
    
    max_k = N + 1
    # Precompute combinations C(k, s) for 0 <= s <= k <= max_k
    comb = [[0] * (max_k + 1) for _ in range(max_k + 1)]
    comb[0][0] = 1
    for k in range(1, max_k + 1):
        comb[k][0] = 1
        comb[k][k] = 1
        for s in range(1, k):
            comb[k][s] = (comb[k-1][s-1] + comb[k-1][s]) % MOD
    
    total = 0
    for k in range(1, N + 2):  # k from 1 to N+1 inclusive
        sum_s = 0
        for s in range(0, k + 1):
            c = comb[k][s]
            sign = (-1) ** s
            term = sign * c
            base = (2 * M - s + 1) % MOD
            term = term * pow(base, N, MOD)
            sum_s = (sum_s + term) % MOD
        sum_s = sum_s % MOD
        total = (total + k * sum_s) % MOD
    
    print(total % MOD)

if __name__ == "__main__":
    main()