> Write an efficient program that given a number, find the integer n that satisfies the above constraints

Goal: Find n where sum of integers from 1 to n-1 is ≤ 30

This is a triangular number problem: (n-1)(n)/2 ≤ 30

... code elided ...

> Ok, now make an find_n_for_sum(s=30)

def find_n_for_sum(s: int) -> int: return int((-(-1) + (1 + 8s)*0.5) / 2)

# Tests assert sum(range(1, find_n_for_sum(30))) <= 30 assert sum(range(1, find_n_for_sum(30) + 1)) > 30