# 第 N 个泰波那契数

<p>泰波那契序列&nbsp;T<sub>n</sub>&nbsp;定义如下：&nbsp;</p>

<p>T<sub>0</sub> = 0, T<sub>1</sub> = 1, T<sub>2</sub> = 1, 且在 n &gt;= 0&nbsp;的条件下 T<sub>n+3</sub> = T<sub>n</sub> + T<sub>n+1</sub> + T<sub>n+2</sub></p>

<p>给你整数&nbsp;<code>n</code>，请返回第 n 个泰波那契数&nbsp;T<sub>n </sub>的值。</p>

<p>&nbsp;</p>

<p><strong>示例 1：</strong></p>

<pre><strong>输入：</strong>n = 4
<strong>输出：</strong>4
<strong>解释：</strong>
T_3 = 0 + 1 + 1 = 2
T_4 = 1 + 1 + 2 = 4
</pre>

<p><strong>示例 2：</strong></p>

<pre><strong>输入：</strong>n = 25
<strong>输出：</strong>1389537
</pre>

<p>&nbsp;</p>

<p><strong>提示：</strong></p>

<ul>
	<li><code>0 &lt;= n &lt;= 37</code></li>
	<li>答案保证是一个 32 位整数，即&nbsp;<code>answer &lt;= 2^31 - 1</code>。</li>
</ul>

<p>以下错误的选项是？</p>

## aop

### before

```cpp

```
### after

```cpp

```

## 答案

```cpp

```

## 选项


### A

```cpp

```

### B

```cpp

```

### C

```cpp

```
