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