This was a ver unintuitive problem, and thanks again to my nephew Karan Sharma on sending this problem. People who sent the correct answers included Abhinav Jain, Pratik Poddar and Suman Saraf.

The answer is 5. It is kind of difficult to explain in words, one needs to see in 3-D, and hence pointing people to a video that shows the answer.

Hope you all enjoyed the puzzle!