Sucessfully added solution of 520B.Two Buttons Codeforces problem

[srcode03]

Please place an x inside the [brackets] in the checklist below

Make sure all the item in the checklist have been done before making the PR

• [ x] You have starred the repo
• [ x] If you have added a new folder, there are no spaces in the name of the folder
• [ x] The link to the problem set is present on the first line of the code file
• [ x] Your code (solution) in your code file(s) is accepted by the problemset on CodeForces

[srcode03]

Kindly review my pull request and let me if changes to be done to it

[virejdasani]

You have changed 121 files and deleted most of them