k = 1
nums1 = [1,2,3,.., 10000]
nums2 = [1,2,3,...,500]
numCounter = {1:1, 2:1, ..., 10000:1}
productCounter = {1:1, 2:1, ..., 500:1}
Loop qua từng product:
product = 1: cands = [1, 2, ... 10000] => loop 10000/1
product = 2: cands = [2, 4, 6, ... 10000] => loop 10000/2
prodcut = 3: cands = [3, 6, 9, ..., 9999] => loop 10000/3
...
product = i: cands = [i, i*2, i*3, ..., i * k] => loop 10000/i
...
product = 500: cands = [500, 500*1, ..., 10000] => loop 10000/500
=> tổng loop = 10000 * (1/1 + 1/2 + ... 1/500)
. Này k dùng chatgpt hơi phí, 
bên e sập r
