diff --git a/16.rkt b/16.rkt
new file mode 100644
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--- /dev/null
+++ b/16.rkt
@@ -0,0 +1,84 @@
+#lang curly-fn racket
+
+(require "scripts/aoc.rkt")
+
+;; solution for day 16
+
+(struct note [name rule0 rule1] #:transparent)
+
+(define (invalid? notes val)
+  (not
+    (for/or ([n (in-list notes)])
+      (match-define (note name (cons a b) (cons c d)) n)
+      (or (and (>= val a) (<= val b)) (and (>= val c) (<= val d))))))
+
+(define (part1 input)
+  (match-define (list notes yours others) input)
+  (for/sum ([tick (in-list others)])
+    (for/sum ([val (in-list tick)] #:when (invalid? notes val)) val)))
+
+(define (part2 input)
+  (match-define (list notes yours others) input)
+  (define (ticket-valid? tick)
+    (not (for/or ([val (in-list tick)]) (invalid? notes val))))
+  (define valid-tickets (filter ticket-valid? others))
+
+  (define mapping (make-hash))
+
+  (for ([idx (in-range (length yours))])
+    (define decided-note (mutable-set))
+    (for ([cand-note (in-list notes)])
+      (define shonks
+        (for/and ([tick (in-list valid-tickets)])
+          (not (invalid? (list cand-note) (list-ref tick idx)))))
+      (when shonks
+        (set-add! decided-note (note-name cand-note))))
+    (when (set-empty? decided-note) (error "couldn't decide..."))
+    (hash-set! mapping idx decided-note))
+
+  ; (displayln mapping)
+
+  (let loop ()
+    (for ([(k v) (in-hash mapping)])
+      (when (= 1 (set-count v))
+        (define fst (set-first v))
+        (for ([k2 (in-list (hash-keys mapping))] #:unless (= k2 k))
+          (set-remove! (hash-ref mapping k2) fst))))
+    (when (for/or ([(k v) (in-hash mapping)])
+            (> (set-count v) 1))
+      (displayln "looping")
+      (loop)))
+  (displayln mapping)
+
+  (for/product ([val (in-list yours)] [idx (in-naturals)])
+    (define n (set-first (hash-ref mapping idx)))
+    (displayln n)
+    (if (string-contains? n "departure")
+      (begin (displayln val) val)
+      1)))
+
+;; parse input file
+(define (parse fname)
+  (match-define (list notes yours others) (string-split (file->string fname) "\n\n"))
+  (define sn string->number)
+  (define pnotes (for/list ([line (in-list (string-split notes "\n"))])
+                   (match line
+                     [(pregexp #px"^([^:]+): (\\d+)\\-(\\d+) or (\\d+)-(\\d+)$"
+                               (list _ name a b c d))
+                      (note name (cons (sn a) (sn b)) (cons (sn c) (sn d)))])))
+  (define pyours (map sn (string-split (second (string-split yours "\n")) ",")))
+  (define pothers (for/list ([line (in-list (rest (string-split others "\n")))])
+                    (map sn (string-split line ","))))
+
+  (list pnotes pyours pothers))
+
+(module+ test
+  (require rackunit)
+  ;; tests here
+  (displayln "no tests :("))
+
+(module+ main
+  (define input (parse "inputs/16"))
+  (answer 16 1 (time (part1 input)))
+  (answer 16 2 (time (part2 input)))
+  (displayln "meow"))