[Solved] Fastest way to solve the divisibility of numbers [closed]

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I propose a mathematical solution.

Number of numbers divided by a is [n/a]. ([] is a floor function.)

And about b, c, lcm(a, b), lcm(a, c), lcm(b, c), lcm(a, b, c) so is it. (lcm means least common multiple.)

So the answer should be 

([n/a]+[n/b]+[n/c])-([n/lcm(a,b)]+[n/lcm(a,c)]+[n/lcm(b,c)])+[n/lcm(a,b,c)]

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solved Fastest way to solve the divisibility of numbers [closed]