from math import comb
H, W = map(int, input().split())
mod = 998244353
ans = 0
for i in range(H + W):
	x = i // 2
	y = i // 2 + i % 2
	if x <= H - 2 and y <= W - 1:
		ans += pow(2, (H - 1) * (W - 1) - i, mod) * comb(H - 2, x) * comb(W - 1, y) % mod
print(ans % mod)