Let's define two functions:
S(N) — sum of all positive numbers not more than N
S(N) = 1 + 2 + 3 + ... + N
Z(N) — sum of all S(i), where 1 <= i <= N
Z(N) = S(1) + S(2) + S(3) + ... + S(N)
You will be given an integer N as input; your task is to return the value of S(Z(N)).
For example, let N = 3:
Z(3) = 1 + 3 + 6 = 10
S(Z(3)) = S(10) = 55
The input range is 1 <= N <= 10^9 and there are 80 ( 40 in LC ) test cases, of which most are
random.