diff --git a/2018/11.rkt b/2018/11.rkt
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+++ b/2018/11.rkt
@@ -0,0 +1,35 @@
+#lang debug br
+(require sugar/cache)
+
+(define (hundreds-digit x)
+  (quotient (modulo x 1000) 100))
+
+(define current-serial (make-parameter 0))
+
+(define/caching (power-at x y)
+  (define rack-id (+ x 10))
+  (- (hundreds-digit (* (+ (* rack-id y) (current-serial)) rack-id)) 5))
+
+(define (grid-scores size-min [size-max size-min])
+  (for*/list ([side (in-range size-min (add1 size-max))]
+              [x (in-range 1 (- 301 side))]
+              [y (in-range 1 (- 301 side))])
+    (list x y
+          (for*/sum ([x (in-range x (+ side x))]
+                     [y (in-range y (+ side y))])
+            (power-at x y)))))
+
+(define (★)
+  (parameterize ([current-serial 7803])
+               (take (argmax third (grid-scores 3)) 2)))
+
+#;(grid-scores 1 300)
+
+#;(define (★★)
+    )
+#;(★★)
+
+(module+ test
+  (require rackunit)
+  #;(check-equal? (time (★)) '(20 51))
+  #;(check-equal? (time (★★)) _))
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