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(import (chicken string))
(import (chicken io))
(import (chicken sort))
(import matchable)
(import srfi-1)
(define input
(with-input-from-file "input"
(lambda ()
(let loop ((ret '()))
(let ((line (read-line)))
(if (eof-object? line)
(reverse ret)
(loop (cons line ret))))))))
(set! input (map string-split input))
(set! input (map (lambda (lst) (map string->number lst)) input))
(define (diff in)
(let loop ((lst in) (ret '()))
(match lst
((a b . r) (loop (cdr lst) (cons (- a b) ret)))
((a) (reverse ret)))))
(define ladder (map diff input))
(define (same-sign in)
(define prod (map (lambda (x) (* x (car in))) in))
(foldl (lambda (a b) (and a b)) #t (map (lambda (x) (> x 0)) prod)))
(define (safe in)
(not (any (lambda (x) (> (abs x) 3)) in)))
(define result
(map (lambda (a b) (and a b))
(map same-sign ladder)
(map safe ladder)))
(display (length (filter (lambda (x) x) result)))
(newline)
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