Facebook CEO Mark Zuckerberg said on Tuesday the social media platform’s efforts to fight back against fake news and verify the authenticity of political advertisements will cost the company billions of dollars, require “tens of thousands” of staff members, and take five to ten years. Zuckerberg said at the “Off the Record” conference in Palo Alto that in the longer term, the company intends to build artificial intelligence systems to complete those tasks. He also said Facebook will verify the authenticity of all “political and issue ads” related to the 2018 midterm elections. “We will always make some mistakes and we will never make it perfect,” said Zuckerberg, whose platform was a hotbed for Russian efforts to impersonate Americans on social media and cause chaos and political divisions ahead of the 2016 U.S. presidential election.