Remote Internship

I offer remote internship to the deserving students. The scheme works this way.

1. You clear an online test for eligibility (given below). You are not eligible for internship until you clear the test.
2. After test clearance, we formulate a problem for you over email.
3. You work on the problem from your home / institute at any time you wish. You update me on issues and progress by email.
4. If you are able to complete the work to my satisfaction, I will ask you for a demo. Otherwise, your internship is wasted.
5. For the demo, you will have to meet me in person, explain me your code and illustrate what it achieves.
6. If I am satisfied with the demo, I will provide you a certificate of internship; otherwise, not.

Eligibility test

We usually have 8 bit characters. I take the binary representation of each character and concatenate all these bits, then I consider each string of six bits in the representation and map it as follows.

0 -> A, 1 -> B, ..., 25 -> Z
26 -> a, 27 -> b, ..., 51 -> z
52 -> 0, 53 -> 1, ..., 61 -> 9
62 -> +, 63 -> /

With the above mapping, I can encode strings. For instance, string madras gets encoded as bWFkcmFz.
Write a program (in any language) to reverse map a string using the above method to find out the original message. When your program is ready, try it on the following message and enter the decoded message in the text box.

Y3Jvc3MgdGhpcyBib3RoIHN1YnRyYWN0aW9uIHNpeCB0aGlydHkgaW5zZXJ0IG9wZW4gdGhlIGRvb3Iw