C# BigInteger Square Root Approximation

bigsqrt.cs

public BigInteger Sqrt(BigInteger n)
        {
            var q = BigInteger.One << ((int)BigInteger.Log(n, 2) >> 1);
            var m = BigInteger.Zero;
            while (BigInteger.Abs(q - m) >= 1)
            {
                m = q;
                q = (m + n / m) >> 1;
            }
            return q;
        }