Given two positive integers a and b, return their least common multiple (LCM) — the smallest positive number divisible by both. The brute-forceBrute ForceChecking multiples of the larger number one at a time until one is also divisible by the smaller number. approach searches directly for the answer. The GCD formulaLCM via GCDThe identity LCM(a, b) × GCD(a, b) = a × b — rearranged to LCM(a, b) = (a / GCD(a, b)) × b, so the fast Euclidean GCD does all the real work. approach skips the search entirely: since a × b always equals LCM × GCD, finding the GCD first (fast, via Find the GCD of Two Numbers) hands over the LCM with one division and one multiplication.