题目描述：
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.
判断一个数是否为ugly number。
对2,3,5执行以下过程：
不断除n，直到无法整除。
最后剩余数字为1，则该数为ugly number。
实现代码：public class Solution {
public bool IsUgly(int num)
{
if(num <= 0){
return false;
}
num = Divide(num,2);
num = Divide(num,3);
num = Divide(num,5);
return num == 1;
}
private int Divide(int num, int a)
{
while(num % a == 0){
num /= a;
}
return num;
}
}