This doesn't happen. Repurchased shares aren't owned by the company, they are effectively retired.
Or put another way, they are owned by the remaining share holders.
You have 100 million shares. Each shareholder owns one hundred millionth part of the company.
The company buys back 50 million shares. Somewhere in their headquarters they have a huge box now with 50 million share certificates. The 50 million remaining shareholders each own one 50 millionth part of the company, including one 50 millionth part of those 50 million share certificates.
If they buy back another 49,999,999 shares, the last shareowner owns the company completely.