878

class Solution:
    def nthMagicalNumber(self, N: int, A: int, B: int) -> int:

        minAB, maxAB = min(A, B), max(A, B)
        while maxAB and minAB:
            rem = maxAB % minAB
            maxAB = minAB
            minAB = rem
        lcm = A * B // maxAB

        l = 1
        r = N * (A + B) + 1

        while r - l > 1:
            mid = l + (r - l) // 2
            res = mid // A + mid // B - mid // lcm
            if res > N or (res == N and mid % A != 0 and mid % B != 0):
                r = mid
            else:
                l = mid

        return l % (10**9 + 7)