## Description #

Difficulty: **简单**

Related Topics: Math, Binary Search

Given a non-negative integer `x`

, return *the square root of* `x`

*rounded down to the nearest integer*. The returned integer should be **non-negative** as well.

You **must not use** any built-in exponent function or operator.

- For example, do not use
`pow(x, 0.5)`

in c++ or`x ** 0.5`

in python.

**Example 1:**

```
Input: x = 4
Output: 2
Explanation: The square root of 4 is 2, so we return 2.
```

**Example 2:**

```
Input: x = 8
Output: 2
Explanation: The square root of 8 is 2.82842..., and since we round it down to the nearest integer, 2 is returned.
```

**Constraints:**

- 0 <= x <= 2
^{31}- 1

## Solution #

Language: **Go**

IOI