you've/it's got me stumped
slang I don't know; I have no idea. Well, you've got me stumped. When did Millard Fillmore become president? Can you help me with this math problem? It's got me stumped.
(You've) got me stumped.
Inf. I can't possibly figure out the answer to your question. Bill: How long is the Amazon River? Jane: You've got me stumped. Bob: Do you know of a book that would interest a retired sea captain? Sally: You've got me stumped.