#define MD 998244353
Comb<Mint>c;
ll@h,@w;
Mint z=h<2;
rep(i,min(2w-1,2h-2))z+=Mint(2)**((h-1)*(w-1)-i)*c.C(w-1,(i+1)/2)*c.C(h-2,i/2);
wt(z);