diff --git a/2023/ruby/day_09.rb b/2023/ruby/day_09.rb
index 3461a7b..b07873e 100644
--- a/2023/ruby/day_09.rb
+++ b/2023/ruby/day_09.rb
@@ -1,26 +1,17 @@
 histories = ARGF.readlines.map { _1.scan(/-?\d+/).map(&:to_i) }
 
-# part one
-p histories
-  .map {|history|
-    diffs = [history]
-    until diffs.last.all?(&:zero?)
-      diffs << diffs.last.each_cons(2).map { _2 - _1 }
-    end
+history_diffs = histories.map {|history|
+  diffs = [history]
+  until diffs.last.all?(&:zero?)
+    diffs << diffs.last.each_cons(2).map { _2 - _1 }
+  end
+  diffs
+}
 
-    diffs.sum(&:last)
-  }
-  .sum
+# part one
+p history_diffs.sum { _1.sum(&:last) }
 
 # part two
-p histories
-  .map {|history|
-    diffs = [history]
-    until diffs.last.all?(&:zero?)
-      diffs << diffs.last.each_cons(2).map { _2 - _1 }
-    end
-
-    diffs.map(&:first).reverse.inject { _2 - _1 }
-  }
-  .sum
-
+p history_diffs.sum {|diffs|
+  diffs.map(&:first).reverse.inject { _2 - _1 }
+}