for(maxsize=1;maxsize*16<w;maxsize*=2);

        maxlevel=maxsize*maxsize;

        x_start=new int[maxlevel];
        y_start=new int[maxlevel];
        sizes=new int[maxlevel];

        for(int i=maxlevel-1;i>=0;i--)
        {
                x_start[i]=y_start[i]=sizes[i]=0;
                for(int j=maxsize/2;j>0;j/=2)
                {
                        int k=i/j/j+1;
                        x_start[i]+=(((k/2)%2)*maxsize)/j/2;
                        y_start[i]+=(((k-1)%2)*maxsize)/j/2;
                        sizes[i]=(k!=1)?MAX(1,sizes[i]):maxsize/j;
                }
        }