ll@H,@W,@N,@K;mint a,S,t,u;a.setmod(998244353);a=H*W;S=(H-K+1)*(W-K+1);rep(i,H){u=0;rep(j,W){t=(1-(max(min(i,H-K)-max(i-K,-1),0)*max(min(j,W-K)-max(j-K,-1),0))/S)**N;if(K<=j<W-K)u+=t*(W-2K),j=W-K-1;else u+=t;}if(K<=i<H-K)a-=u*(H-2K),i=H-K-1;else a-=u;}wt(a);