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# 1259. Handshakes That Don't Cross

<https://leetcode.com/problems/handshakes-that-dont-cross>

## Description

You are given an **even** number of people `num_people` that stand around a circle and each person shakes hands with someone else, so that there are `num_people / 2` handshakes total.

Return the number of ways these handshakes could occur such that none of the handshakes cross.

Since this number could be very big, return the answer **mod `10^9 + 7`**

**Example 1:**

```
**Input:** num\_people = 2
**Output:** 1
```

**Example 2:**

![](https://assets.leetcode.com/uploads/2019/07/11/5125_example_2.png)

```
**Input:** num\_people = 4
**Output:** 2
**Explanation:** There are two ways to do it, the first way is [(1,2),(3,4)] and the second one is [(2,3),(4,1)].
```

**Example 3:**

![](https://assets.leetcode.com/uploads/2019/07/11/5125_example_3.png)

```
**Input:** num\_people = 6
**Output:** 5
```

**Example 4:**

```
**Input:** num\_people = 8
**Output:** 14
```

**Constraints:**

* `2 <= num_people <= 1000`
* `num_people % 2 == 0`

## ac

```java
```