How to install CRAN R on Raspbian Raspberry Pi

For my telegram bot project I want to use the CRAN R on my old Raspberry Pi 2. I've already wrote about using of R telegram package earlier. The problem is that the package require the latest R version and we have only old 3.1.1 in the Raspbian Jessie repository by default.
I've tried a lot of ways to solve that. The easiest in my opinion is to add the following repository into /etc/apt/sources.list

deb http://archive.raspbian.org/raspbian/ stretch main

Thus we'll add testing packages like the latest R.
Don't forget to update apt repository with

# apt-get update

 Enjoy