function cannot_hit=b_dxball(n,positon,start)

hit=0;

for i=1:1:n
    %odd-odd or even_case
    if(  ( (rem(start(1),2)==0 && rem(start(2),2)==0) || (rem(start(1),2)==1 && rem(start(2),2)==1) ) )
        if(  (rem(position(i,1),2)==0 && rem(position(i,2),2)==0) || (rem(position(i,1),2)==1 && rem(position(i,2),2)==1) )
        hit = hit + 1;
        end

        %odd_even case
    elseif( ( (rem(start(1),2)==0 && rem(start(2),2)==1) || (rem(start(1),2)==1 && rem(start(2),2)==0) ) )
        if(rem(position(i,1),2)==0 && rem(position(i,2),2)==1) || (rem(position(i,1),2)==1 && rem(position(i,2),2)==0)
        hit = hit + 1;
        end
    end

end

cannot_hit = n - hit;

end