Say for example I wish to install the latest Debian package "libgcc1" for Jessie on AMD64.

How can I determine the correct URL to download from <https://packages.debian.org> 

For example, in this case, clicking manually through the <https://packages.debian.org> website gets me ultimately to the correct download, which is:

<http://ftp.us.debian.org/debian/pool/main/g/gcc-4.9/libgcc1_4.9.2-10_amd64.deb>

IMPORTANT NOTE:
I do NOT have apt available. I am writing some code that manually extracts the dependency names from .deb packages, but I am now stuck trying to work out the next steps, which is to get the correct actual .deb package for the package name.

So for example I need to go from these bits of information:

* package name: libgcc1
* version: latest
* architecture: amd64
* debian release: jessie

to:

<http://ftp.us.debian.org/debian/pool/main/g/gcc-4.9/libgcc1_4.9.2-10_amd64.deb>

How can I determine this relationship?

EDIT: for all the people asking "Why not use apt?", the answer is that the core problem I am trying to solve is to install apt. I can't use apt because I am trying to install apt.

thanks