#### Least Common Multiple

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```import unittest
from timeit import timeit

def least_common_multiple_slow(first_num: int, second_num: int) -> int:
"""
Find the least common multiple of two numbers.

>>> least_common_multiple_slow(5, 2)
10
>>> least_common_multiple_slow(12, 76)
228
"""
max_num = first_num if first_num >= second_num else second_num
common_mult = max_num
while (common_mult % first_num > 0) or (common_mult % second_num > 0):
common_mult += max_num
return common_mult

def greatest_common_divisor(a: int, b: int) -> int:
"""
Calculate Greatest Common Divisor (GCD).
see greatest_common_divisor.py
>>> greatest_common_divisor(24, 40)
8
>>> greatest_common_divisor(1, 1)
1
>>> greatest_common_divisor(1, 800)
1
>>> greatest_common_divisor(11, 37)
1
>>> greatest_common_divisor(3, 5)
1
>>> greatest_common_divisor(16, 4)
4
"""
return b if a == 0 else greatest_common_divisor(b % a, a)

def least_common_multiple_fast(first_num: int, second_num: int) -> int:
"""
Find the least common multiple of two numbers.
https://en.wikipedia.org/wiki/Least_common_multiple#Using_the_greatest_common_divisor
>>> least_common_multiple_fast(5,2)
10
>>> least_common_multiple_fast(12,76)
228
"""
return first_num // greatest_common_divisor(first_num, second_num) * second_num

def benchmark():
setup = (
"from __main__ import least_common_multiple_slow, least_common_multiple_fast"
)
print(
"least_common_multiple_slow():",
timeit("least_common_multiple_slow(1000, 999)", setup=setup),
)
print(
"least_common_multiple_fast():",
timeit("least_common_multiple_fast(1000, 999)", setup=setup),
)

class TestLeastCommonMultiple(unittest.TestCase):
test_inputs = [
(10, 20),
(13, 15),
(4, 31),
(10, 42),
(43, 34),
(5, 12),
(12, 25),
(10, 25),
(6, 9),
]
expected_results = [20, 195, 124, 210, 1462, 60, 300, 50, 18]

def test_lcm_function(self):
for i, (first_num, second_num) in enumerate(self.test_inputs):
slow_result = least_common_multiple_slow(first_num, second_num)
fast_result = least_common_multiple_fast(first_num, second_num)
with self.subTest(i=i):
self.assertEqual(slow_result, self.expected_results[i])
self.assertEqual(fast_result, self.expected_results[i])

if __name__ == "__main__":
benchmark()
unittest.main()
```