How to calcualte the average of several plaintexts with Paillier homomorphic encryption?

I am trying to do some calculations with the Paillier Homomorphic encryption scheme. Specifically, given three plain text integers, x1, x2,and x3. I want to first encrypt them, getting their corresponding ciphertexts, say c1, c2 and c3. I want to find the results of (x1+x2+x3)/3 by utilizing c1, c2, c3 and the homomorphic property of Paillier.

I found a post here, which was answered quite a long time ago. When I try the toy example in the accepted answer in this link myself, I can not get the provided result. Specifically, for the following step:

I can calculate the value of k^(-1) mod N with powermod function correctly, but I can not calculate [\mu] correctly. Here is what I did:

1. Say temp = powermod(k, -1, N), Calculate A = powermod(c1*c2*c3, temp, N^2).
2. Calculate B = powermod(r, N, N^2).
3. Calculate [\mu] = mod(A*B, N^2).

This gives me wrong results, I also try replacing powermod with mod, but this time the answer is going to NaN.

Can anyone help me with this, please? Thanks in advance!

Mathlab is not directly adequate for the large integers used in public-key crypto.

Reading The Fine Manual shows there is a limit of $2^{64}$. Even $c_1\cdot c_2$ exceeds that.

Python, SageMath, Mathematica, and many other languages have no such limitation. That makes them adequate for experimenting with the math in public-key crypto (but not necessarily implementation of public-key crypto when it comes to adequate speed, or resisting side-channel attacks).

Not sure precisely which language you're using, but the intermediate values should be

temp=206674

A=284095452063

B=144829438301

and the calculation works fien for me.