I have learnt Gaussian algorithm recently. I am stacked in 251D - Two Sets.

I have read the editorial of this problem. I can find the max value of X1+X2. But in case of tie. I am not getting how to check is it good to give 0 in i-th bit of X1 when i-th bit of X is 1 and also not understanding how give 0 in i-th bit. I have saw some Ac code but I am not getting what they have done. So please can any one tell me how can I do it.

Thanks in advance. :)