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 (such as `Math.sqrt` or `**` or `x ** 0.5`).
Example 1
Input:x = 4
Output:2
Explanation:The square root of 4 is 2.
Example 2
Input:x = 8
Output:2
Explanation:The square root of 8 is 2.828..., rounded down to 2.