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# 1608. Special Array With X Elements Greater Than or Equal X

<https://leetcode.com/problems/special-array-with-x-elements-greater-than-or-equal-x>

## Description

You are given an array `nums` of non-negative integers. `nums` is considered **special** if there exists a number `x` such that there are **exactly** `x` numbers in `nums` that are **greater than or equal to** `x`.

Notice that `x` **does not** have to be an element in `nums`.

Return `x` *if the array is **special**, otherwise, return* `-1`. It can be proven that if `nums` is special, the value for `x` is **unique**.

**Example 1:**

```
**Input:** nums = [3,5]
**Output:** 2
**Explanation:** There are 2 values (3 and 5) that are greater than or equal to 2.
```

**Example 2:**

```
**Input:** nums = [0,0]
**Output:** -1
**Explanation:** No numbers fit the criteria for x.
If x = 0, there should be 0 numbers >= x, but there are 2.
If x = 1, there should be 1 number >= x, but there are 0.
If x = 2, there should be 2 numbers >= x, but there are 0.
x cannot be greater since there are only 2 numbers in nums.
```

**Example 3:**

```
**Input:** nums = [0,4,3,0,4]
**Output:** 3
**Explanation:** There are 3 values that are greater than or equal to 3.
```

**Example 4:**

```
**Input:** nums = [3,6,7,7,0]
**Output:** -1
```

**Constraints:**

* `1 <= nums.length <= 100`
* `0 <= nums[i] <= 1000`

## ac

```java
```