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Solution: Nth Magical Number

Explore how to determine the nth magical number, defined as a positive integer divisible by either a or b, by applying the inclusion-exclusion principle and a binary search algorithm. Understand how to count multiples efficiently, compute the least common multiple, and optimize your solution within given constraints, all while keeping time complexity to a logarithmic scale.

Statement

Given three integers n, a, and b, return the nth magical number.

A magical number is defined as a positive integer that is divisible by either a or b.

As the result may be very large, return it modulo 109+710^9+7.

Constraints:

  • 11 \leq n 109\leq 10^9

  • ...