This is my approach for Roads to Chefland in CookOff 2020. I found a pattern and wrote the code accordingly. The time complexity of this code is O(log(n)).
Link to Problem Statement
Link to my formatted code
Have a look at my code, any feedback would be great ! 
Can someone tell what’s wrong in this code.
It’s showing wrong answer on submission.
What’s the idea behind function funn ?
There’s no idea behind it
there must be some logic in using these 2 lines, if u would explain it then it would be better for me to find where it went wrong !
count=(a*((n-a)//(2*a)))+b
count=count+a
First line is combing all odd multiples of power of 2 and second line is connecting that 2^k node to 1st one.