sqrt

double mysqrt(double x)
{
    double l = 0, r = x, mid;
    for (int i = 0; i < 1e3; i++)
    {
        mid = (l + r) / 2;
        if (mid * mid == x)
            return mid;
        else if (mid * mid > x)
            r = mid;
        else
            l = mid;
    }

    return mid;
}