Chess players that have never lost to an AI is 40/4 = <<40/4=10>>10 people.

Chess players that have lost to an AI is 40-10 = <<40-10=30>>30 people.

# Answer

30
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
On the island of Castor, there are 40 chess players. A quarter of the island's chess players have never lost to an AI. How many people on the island have lost to a computer, at least once?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
30
On the island of Castor, there are 40 chess players. A quarter of the island's chess players have never lost to an AI. How many people on the island have lost to a computer, at least once?
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