Hello all! :)
I stumbled upon this problem but I do not know how to solve it.
http://www.spoj.com/problems/ADDLCM/
The sum can be written as
![](https://espresso.codeforces.com/0931dc007b8e9649a38ca18383ae4cd46cbb30fe.png)
but this doesn't make the problem any easier. I can evaluate the first sum but its not easy to evaluate the second. Please give me some ideas to solve this.
Any help is appreciated. Thanks!