#define MD 998244353
ll@H,@W,@A,@B;Mint S=(H-A+1)*(W-B+1);auto f=[S](ll h,ll k){return(2k>h?(h-k)*(h-k+1)+(2k-h)*(h-k+1):k*(k-1)+(h-2k+2)*k)/S;};auto g=[S](ll h,ll k){return(2k>h?(h-k)*(h-k+1)*(2h-2k+1)/3+(2k-h)*(h-k+1)**2:(k-1)*k*(2k-1)/3+(h-2k+2)*k*k)/S;};S=2S*f(H,A)*f(W,B)-g(H,A)*g(W,B);wt(S);