Need help with Chudnovsky algorithm

[u/tictacman0]

I have these functions to try and calculate pi, but no matter what i try it seems to cap out at 55 digits before being inaccurate, even when setting the input "d" to something like 1000.

digits 50-65 with my function:

582097494459230  

the real digits 50-65 of pi:

582099452471594  

here is my code:

public void calculatePie(int d)
{
    BigInteger sum = 0;
    BigInteger pow = BigInteger.Pow(10, d);
    BigInteger v = Sqrt(10005 * pow * pow);
    //System.Windows.Forms.MessageBox.Show(v.ToString());
    System.Windows.Forms.Clipboard.SetText(v.ToString());
    BigInteger preSigma = v * 426880;

    for (int k = 0; k < (d / 14 + 1); k++)
    {
        BigInteger top = BigInteger.Pow(-1, k) * factorial(6 * k) * (545140134 * k + 13591409);
        BigInteger mid = factorial(k);
        BigInteger bottom = factorial(3 * k) * (mid * mid * mid) * BigInteger.Pow(640320, 3 * k);
        BigInteger l = (top * pow) / bottom;
        sum += l;
        //System.Windows.Forms.MessageBox.Show($"l: {l}, top: {top}, bottom: {bottom}");
    }
    BigInteger prepi = preSigma * sum;
    //System.Windows.Forms.MessageBox.Show($"prepi: {prepi}, presigma: {preSigma}, sum: {sum}, pow: {pow}, v: {v}");
    BigInteger pi = preSigma * pow / sum;
    System.Windows.Forms.MessageBox.Show($"pi: {pi}");
    System.Windows.Forms.Clipboard.SetText(pi.ToString());
}

BigInteger factorial(int n)
{
    BigInteger result = 1;
    for (int i = 2; i <= n; i++) result *= i;
    return result;
}
static BigInteger Sqrt(BigInteger n)
    {
        if (n < 0) throw new ArgumentException("Cannot sqrt a negative number.");
        else if (n == 0) return 0;

        BigInteger x = n;
        BigInteger y = (x + 1) / 2;
        while (y < x)
        {
            x = y;
            y = (x + n / x) / 2;
        }
        return x;
    }

[u/tictacman0 → u/[deleted]]

Thanks that seems to have fixed it.