diff --git a/25.rkt b/25.rkt
new file mode 100644
index 0000000..abed557
--- /dev/null
+++ b/25.rkt
@@ -0,0 +1,53 @@
+#lang curly-fn racket
+
+(require "scripts/aoc.rkt")
+
+;; solution for day 25
+
+(define *mod* 20201227)
+
+(define (loop subject times)
+  (for/fold ([val 1]) ([_ (in-range (+ 0 times))])
+    (remainder (* val subject) *mod*)))
+
+(define (part1 input)
+  (match-define (list you door) input)
+  (define you-loops #f)
+  (define door-loops #f)
+  (for/fold ([val 1]) ([loops (in-range 0 +inf.0)] #:break (and you-loops door-loops))
+    (when (= val you)
+      (set! you-loops loops))
+    (when (= val door)
+      (set! door-loops loops))
+    (remainder (* val 7) *mod*))
+  ; (displayln you-loops)
+  ; (displayln door-loops)
+  (displayln you-loops)
+  (displayln (loop 7 you-loops))
+  (displayln you)
+  (displayln door-loops)
+  (displayln (loop 7 door-loops))
+  (displayln door)
+  ; (displayln (loop door-loops you-loops))
+  ; (displayln (loop you-loops door-loops))
+  ; (displayln (loop 17807724 8))
+  ; (displayln (loop 5764801 11))
+  (loop you door-loops))
+; (part1 (list 5764801 17807724))
+; (error)
+
+;; parse input file
+(define (parse fname)
+  (define input (file->lines fname))
+  (map string->number input))
+
+(module+ test
+  (require rackunit)
+  ;; tests here
+  (displayln "no tests :("))
+
+(module+ main
+  (define input (parse "inputs/25"))
+  (answer 25 1 (time (part1 input)))
+  (aoc-finish)
+  (displayln "meow"))
diff --git a/scripts/aoc-lib.rkt b/scripts/aoc-lib.rkt
index 7a9ec19..1ef6fef 100644
--- a/scripts/aoc-lib.rkt
+++ b/scripts/aoc-lib.rkt
@@ -73,6 +73,9 @@
      'answer-correct]
     [(pregexp #px"That's not the right answer") 'answer-incorrect]
     [(pregexp #px"You gave an answer too recently") 'rate-limited]
+    [(pregexp #px"fifty stars")
+     (aoc-set-complete! day part)
+     'year-complete]
     [(pregexp #px"Did you already complete it?")
      (aoc-set-complete! day part)
      'already-completed]
diff --git a/scripts/aoc.rkt b/scripts/aoc.rkt
index b4c4494..4638154 100644
--- a/scripts/aoc.rkt
+++ b/scripts/aoc.rkt
@@ -3,7 +3,7 @@
 ;; utilities for every challenge script
 
 (require "aoc-lib.rkt" threading syntax/parse/define (for-syntax racket/syntax) graph)
-(provide answer dbg memoize define/memoized
+(provide answer aoc-finish dbg memoize define/memoized
          band bor bxor bnot bshl bshr bset? bfield
          maximum-bipartite-matching/stable
          (all-from-out threading syntax/parse/define graph)
@@ -63,3 +63,13 @@
                             (~a answer)))
        (printf "server responded: ~a\n" resp)]
       [_ (printf "not submitting\n")])))
+
+;; submit 25 part 2
+(define (aoc-finish)
+  (unless (aoc-complete? 25 1)
+    (error "submit 25.1 first"))
+  (unless (aoc-complete? 25 2)
+    (printf "submitting done for 25.2...\n")
+    (define resp
+      (aoc-submit-answer (getenv "AOC_YEAR") "25" (getenv "AOC_SESSION") "2" "done"))
+    (printf "server responded: ~a\n" resp)))