Given a non-negative integer `x`, compute and return the square root of `x`.

Since the return type is an integer, the decimal digits are truncated, and only the integer part of the result is returned.

Note: You are not allowed to use any built-in exponent function or operator, such as `pow(x, 0.5)` or `x ** 0.5`.

Example 1:

    Input: x = 4
    Output: 2

Example 2:

    Input: x = 8
    Output: 2
    Explanation: The square root of 8 is 2.82842..., and since the decimal part is truncated, 2 is returned.

Constraints:

- `0 <= x <= 231 - 1`