diff --git a/2023/ruby/day_15.rb b/2023/ruby/day_15.rb
new file mode 100644
index 0000000..24bc487
--- /dev/null
+++ b/2023/ruby/day_15.rb
@@ -0,0 +1,12 @@
+input = ARGF.read.strip.split(?,).map(&:chars)
+
+# part one
+p input.sum {|str|
+  current = 0
+  str.each do |c|
+    current += c.ord
+    current *= 17
+    current %= 256
+  end
+  current
+}