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# 263. Ugly Number

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 × 3
```

**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. `1` is typically treated as an ugly number.
2. Input is within the 32-bit signed integer range: \[−231,  231 − 1].

```
# @param {Integer} num
# @return {Boolean}
def is_ugly(num)
  return false if num == 0
  while num % 2 == 0
    num = num / 2
  end
  while num % 3 == 0
    num = num / 3
  end
  while num % 5 == 0
    num = num / 5
  end
  num == 1
end
```