Write a program to check whether a given number is an ugly number.
Ugly numbers are positive numbers whose prime factors only include 2, 3, 5.
Example 1:
Input: 6
Output: true
Explanation: 6 = 2 × 37
Example 2:
Input: 8
Output: true
Explanation: 8 = 2 × 2 × 2
Example 3:
Input: 14
Output: false
Explanation: 14 is not ugly since it includes another prime factor 7.
Note:
1 is typically treated as an ugly number.
Input is within the 32-bit signed integer range: [−231, 231 − 1].
思路：把2、3、5这些因数全部删除、看最后是否等于1即可
