from functools import reduce
from time import time
def gcd(a, b):
while b:
a, b = b, a%b
return a
def lcm(a, b):
return a * b // gcd(a, b)
t1 = time()
print(reduce(lcm, range(1, 21)))
t2 = time()
print("time elapsed:", t2 - t1)
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