4个一组蛋糕方阵，相邻4个一组的空白方阵

贪心：4个一组蛋糕方阵，相邻4个一组的空白方阵，交替摆放即可：

import java.util.*;
public class Main {
    public static void main(String[] args) throws Exception{
        Scanner sc = new Scanner(System.in);
        int W = sc.nextInt(), H = sc.nextInt();
        if(W <= 2 && H <= 2) {
            System.out.println(W*H);
            return;
        }
        if(W <= 2){
            int temp = W;
            W = H;
            H = temp;
        }
        int r = 0, a = W/2, b = W%2;
        if(b == 1) a++;
        int len1 = a, len2 = a - 1;
        r += H/4*2*W;
        if(H%4 == 1) r += len1;
        if(H%4 == 2) r += 2*len1;
        if(H%4 == 3) r += len1 + W;
        System.out.println(r);
    }
}