This is has happened 2nd or 3rd time, that contest has been declared unrated due to picking problems from other platforms. Please make sure that problems are original beforehand. There goes a lot of effort in solving them and then finding that contest has been declared unrated just breaks the heart :( .

Excellent Contest. I think observations are important for CP rather than implementing the same algorithms continuously in more or less the same way to solve the questions. All Of CP is actually Mathematics only so I personally liked all the problems.

The numbers that we need to form should have distinct powers and their coefficient should be either 1 or 0. For example if we take n = 4 and k = 17 then 17 = (10) base 4. So this would give an intuition that we need to do something with binary strings or bianry representation of a number K as we need coefficient as 0 or 1 of the powers. Now Lets see what we have to do K = 1 in binary = 1 K = 2 in binary = 10 K = 3 in binary = 11 K = 4 in binary = 100 and so on Now lets see how our answer comes out, As we need to find the Kth special number for base n so suppose that above binary strings were formed with base n and then convert them into their decimal equivalent respectively. For example from test cases where n = 3 and k = 4 so now binary representaion of k is 100. Just take this in base n = 3 so it comes out to be 1*3^2 + 0*3^1 + 0*3^0 = 9 and our answer. Similarly take n = 2 and k = 12. So 12 = 1100 in binary. As our base n is also 2 only answer again converts back to 12. You can further take more examples.

Great set of problems with good underlying logics.

Excellent material for cp.