H, W = map(int, input().split())
if H == 1 or W == 1:
	exit(print(1))
mod = 998244353
ans = 0
ch = 1
cw = 1
for i in range(H + W - 2):
	x = i // 2
	y = i // 2 + i % 2
	if x <= H - 2 and y <= W - 1:
		if x == y:
			if x:
				ch = ch * (H - x - 1) * pow(x, mod - 2, mod) % mod
		else:
			if y:
				cw = cw * (W - y) * pow(y, mod - 2, mod) % mod
		ans += pow(2, (H - 1) * (W - 1) - i, mod) * ch * cw % mod
print(ans % mod)