ll@H,@W,@N,@K;modint a=H*W,S=(H-K+1)*(W-K+1);a.setmod(998244353);rep(i,H)rep(j,W){a-=(1-(max(min(i,H-K)-max(i-K,-1),0)*max(min(j,W-K)-max(j-K,-1),0))/S).pw(N);}wt(a);