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. For example, 6, 8 are ugly while 14 is not ugly since it includes another prime factor 7.
Note that 1 is typically treated as an ugly number.
如果这个数只有2，3，5这三个质数约数，则为ugly number。换句话说，ugly number一定是且只能是2，3，5这三个数自由组合的乘积。