diff --git a/4.rkt b/4.rkt
new file mode 100644
index 0000000..d5139dc
--- /dev/null
+++ b/4.rkt
@@ -0,0 +1,88 @@
+#lang curly-fn racket
+
+(require "scripts/aoc.rkt")
+
+;; solution for day 4
+
+;; helper functions here
+(struct passport [byr iyr eyr hgt hcl ecl pid cid] #:transparent)
+
+(define (part1 input)
+  (define pp-valid?
+    (struct/c passport string? string? string? string? string? string? string? any/c))
+  (for/sum ([pp (in-list input)] #:when (pp-valid? pp)) 1))
+
+(define (part2 input)
+  (define ((strlen/c num) str)
+    (= (string-length str) num))
+
+  (define ((strnum-range/c low high) s)
+    (define sn (string->number s))
+    (and (number? sn)
+         (<= low sn high)))
+
+  (define (height/c hs)
+    (match hs
+      [(pregexp #px"([0-9]+)cm" (list _ h)) ((strnum-range/c 150 193) h)]
+      [(pregexp #px"([0-9]+)in" (list _ h)) ((strnum-range/c 59 76) h)]
+      [_ #f]))
+
+  (define (hcolor/c cs)
+    (match cs
+      [(pregexp #px"#[0-9a-f]{6}") #t]
+      [_ #f]))
+
+  (define (ecolor/c cs)
+    (match cs
+      [(or "amb" "blu" "brn" "gry" "grn" "hzl" "oth") #t]
+      [_ #f]))
+
+  (define pp-valid?
+    (struct/c passport
+              (and/c string? (strlen/c 4) (strnum-range/c 1920 2002))
+              (and/c string? (strlen/c 4) (strnum-range/c 2010 2020))
+              (and/c string? (strlen/c 4) (strnum-range/c 2020 2030))
+              (and/c string? height/c)
+              (and/c string? hcolor/c)
+              (and/c string? ecolor/c)
+              (and/c string? (strlen/c 9) (strnum-range/c 0 999999999))
+              any/c))
+  (for/sum ([pp (in-list input)] #:when (pp-valid? pp)) 1))
+
+(module+ test
+  (require rackunit)
+  ;; tests here
+  (displayln "no tests :("))
+
+(module+ main
+  (define input-lines (file->lines "inputs/4"))
+
+  (define input
+    (for/fold ([input (list (passport #f #f #f #f #f #f #f #f))]) ([line (in-list input-lines)])
+      (define pp (first input))
+      (cond
+        [(zero? (string-length line)) (cons (passport #f #f #f #f #f #f #f #f) input)]
+        [else
+         (define parts (string-split line " "))
+         (define new-pp
+           (for/fold ([new-pp pp]) ([part (in-list parts)])
+             (match-define (list name val) (string-split part ":"))
+             (match name
+               ["byr" (struct-copy passport new-pp [byr val])]
+               ["iyr" (struct-copy passport new-pp [iyr val])]
+               ["eyr" (struct-copy passport new-pp [eyr val])]
+               ["hgt" (struct-copy passport new-pp [hgt val])]
+               ["hcl" (struct-copy passport new-pp [hcl val])]
+               ["ecl" (struct-copy passport new-pp [ecl val])]
+               ["pid" (struct-copy passport new-pp [pid val])]
+               ["cid" (struct-copy passport new-pp [cid val])]
+               [_ (error "not shonks" line name val)])))
+         (cons new-pp (rest input))])))
+
+  ;; part 1
+  (answer 4 1 (part1 input))
+
+  ;; part 2
+  (answer 4 2 (part2 input))
+
+  (displayln "meow"))