# 1641. Count Sorted Vowel Strings

<https://leetcode.com/problems/count-sorted-vowel-strings>

## Description

Given an integer `n`, return *the number of strings of length* `n` *that consist only of vowels (*`a`*,* `e`*,* `i`*,* `o`*,* `u`*) and are **lexicographically sorted**.*

A string `s` is **lexicographically sorted** if for all valid `i`, `s[i]` is the same as or comes before `s[i+1]` in the alphabet.

**Example 1:**

```
**Input:** n = 1
**Output:** 5
**Explanation:** The 5 sorted strings that consist of vowels only are ["a","e","i","o","u"].
```

**Example 2:**

```
**Input:** n = 2
**Output:** 15
**Explanation:** The 15 sorted strings that consist of vowels only are
["aa","ae","ai","ao","au","ee","ei","eo","eu","ii","io","iu","oo","ou","uu"].
Note that "ea" is not a valid string since 'e' comes after 'a' in the alphabet.
```

**Example 3:**

```
**Input:** n = 33
**Output:** 66045
```

**Constraints:**

* `1 <= n <= 50`

## ac

```java
```