0. #lang racket
1.  
2. (define (build-phonebook)
3.   (for/hasheq ([i (in-range (read))])
4.     (values (read) (read))))
5.  
6. (let ([phonebook (build-phonebook)])
7.   (for ([query (in-port)])
8.     (displayln
9.       (let ([maybe-phone (hash-ref phonebook query #f)])
10.         (if maybe-phone
11.             (format "~a=~a" query maybe-phone)
12.             "Not found")))))

=>

in-range: contract violation

expected: real?

given: #<eof>