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+(load "lib")
+
+(defparameter input (uiop:read-file-string "10-input"))
+(defparameter lines (get-lines input))
+
+(defun parse-line (line)
+  (destructuring-bind (op . operand)
+      (--> (string-to-clist line)
+           (split-by-completely it #\Space)
+           (mapcar #'clist-to-string it))
+    (if (string= op "noop")
+        '(noop . nil)
+        `(add . ,(parse-integer (car operand))))))
+
+(defparameter important-cycles (list 20 60 100 140 180 220))
+
+(defun check-sum (sum cycles x)
+  (if (member cycles important-cycles)
+      (+ sum (* cycles x))
+      sum))
+
+(let ((sum 0))
+  (loop with x = 1
+        for cycles from 1
+        for line in lines
+        for (op . operand) = (parse-line line)
+        if (eq op 'noop)
+          do (setq sum (check-sum sum cycles x))
+        else
+          do (setq sum (check-sum sum cycles x)
+                   cycles (+ cycles 1)
+                   sum (check-sum sum cycles x)
+                   x (+ x operand)))
+  (format t "Round 1: ~a~%" sum))
+
+(let ((lit-pixels nil))
+  (defun update-pixels (x cycles)
+    (let ((cycles (mod (- cycles 1) 40)))
+      (push
+       (if (or (= cycles (+ x 1))
+               (= cycles x)
+               (= cycles (- x 1)))
+           "#"
+           ".")
+       lit-pixels)))
+
+  (loop with x = 1
+        for cycles from 1
+        for line in lines
+        for (op . operand) = (parse-line line)
+        if (eq op 'noop)
+          do (update-pixels x cycles)
+        else
+          do (update-pixels x cycles)
+          and do (setq cycles (+ cycles 1))
+          and do (update-pixels x cycles)
+          and do (setq x (+ x operand)))
+
+  (setq lit-pixels (reverse lit-pixels))
+
+  (format t "Round 2: ")
+  (loop for pixel in lit-pixels
+        for cycle from 0
+        if (= (mod cycle 40) 0)
+          do (format t "~%")
+        do
+        (format t "~a" pixel)))