from typing import List


def find_dup_brute_force(numbers: List) -> int:
	"""
	Solution: Brute force double iteration.
	Complexity:
		Time: O(n^2) - Iterate through our list twice
		Space: O(1) - Storing a single boolean
	"""
	for num1 in numbers:
		num_found = False
		for num2 in numbers:
			if num1 == num2:
				if num_found:
					return num1
				else:
					num_found = True
	raise Exception("No duplicates found")