878. Nth Magical Number

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

 

Constraints:

• 1 <= n <= 109
• 2 <= a, b <= 4 * 104