Automatically add people to facebook group

Avg Bid (INR)
Project Budget (INR)
₹600 - ₹1500

Project Description:
I have been added several times to facebook groups I do not even know. For curiosity I went on them and saw that some of these had even over a million group members. The only explanation for me is that they use some sort of robot to add members to these groups. How do they do it?
Can you develop a mechanism that can add people to my facebook page without someone manually being involved? I can provide a screenshot of that group that added me and has hundreds of thousands of group members. I have a list of contacts but adding/inviting them manually would be too tedious.
Thank you

Skills required:
Facebook Marketing, Internet Marketing, Link Building, SEO
Qualifications required:
us_eng_1 US English - Level 1
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₹ 1300
in 3 days
₹ 20000
in 30 days