You need to solve the A.G.P :
<span>Σ</span>
(A + i * d)*X<sup>N-i</sup>
EXPLAINATION:
It is a simple mathematics question. Here, you need to calculate the sum mod 215372682525 as mentioned above.
But, keep in mind that 215372682525^2 = 46385392378014440375625, which is greater than 2^64. Therefore, all
you need to do is calculate the value of x^0, x^1, x^2, x^3, x^4, …, x^n and simultaneously take the mod with 215372682525 and
save the mod value at corresponding index i. Similarly, do the same for a + id for each value of i and save the mod value at
corresponding index i. Now, multiply a + id with the corresponding x^(n-i) value and take the mod and save the mod value at
corresponding index i. Finally, add them and simultaneously take the mod.