0878. Nth Magical Number

https://leetcode.com/problems/nth-magical-number

Description

A positive integer is magical if it is divisible by either a or b.

Given the three integers n, a, and b, return the nth magical number. Since the answer may be very large, return it modulo 109 + 7.

Example 1:

**Input:** n = 1, a = 2, b = 3
**Output:** 2

Example 2:

**Input:** n = 4, a = 2, b = 3
**Output:** 6

Example 3:

**Input:** n = 5, a = 2, b = 4
**Output:** 10

Example 4:

**Input:** n = 3, a = 6, b = 4
**Output:** 8

Constraints:

• 1 <= n <= 109

• 2 <= a, b <= 4 * 104

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