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#lang racket
(require threading)
(define input (file->lines "input"))
(define (map-differing-lengths f . arrs)
(define minLength (apply min (map length arrs)))
(define newLists (map (lambda (x) (take x minLength)) arrs))
(apply map (cons f newLists)))
(define (build-windows xs)
(map-differing-lengths list xs (cdr xs) (drop xs 2)))
(define (diff-pairs xs)
(map-differing-lengths - (cdr xs) xs))
(~>> input
(map string->number)
(build-windows)
(map (lambda (x) (apply + x)))
(diff-pairs)
(filter positive?)
(length _))
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