Hide

Problem B
Bus Numbers

/problems/busnumbers2/file/statement/en/img-0001.jpg
A bus with a number that is not a bus number according to our definition. License: public domain
A famous story about the mathematicians G.H. Hardy and Srinivasa Ramanujan goes as follows (as told by Hardy):
I remember once going to see him (Ramanujan) when he was lying ill at Putney. I had ridden in taxicab No. 1729, and remarked that the number seemed to be rather a dull one, and that I hoped it was not an unfavourable omen. “No”, he replied, “it is a very interesting number; it is the smallest number expressible as the sum of two [positive] cubes in two different ways.”

It is from this story the taxicab numbers got their name. The n’th taxicab numbers is defined to be the smallest number that can be expressed as a sum of two positive cube numbers in n distinct ways.

It turns out that these numbers grows rather quickly. This makes them very hard to compute, which is not very fun. A variation of the concept is to consider what we will call the bus numbers – all the numbers which can expressed as the sum of two positive cube numbers in at least 2 distinct ways. Note that according to this definition, all taxicab numbers (except the first) are also bus numbers.

Your task is to write a program that generates bus numbers; in particular, the largest bus number that is at most equal to some limit m.

Input

The input consists of:

  • one line with an integer m (1m400000), the upper bound of the bus number.

Output

Output the largest bus number x which does not exceed m. If there is no such number, output none.

Sample Input 1 Sample Output 1
1730
1729
Sample Input 2 Sample Output 2
100
none
Hide

Please log in to submit a solution to this problem

Log in