diff --git a/AdventOfCode2023.FSharp/AdventOfCode2023.FSharp.Lib/AdventOfCode2023.FSharp.Lib.fsproj b/AdventOfCode2023.FSharp/AdventOfCode2023.FSharp.Lib/AdventOfCode2023.FSharp.Lib.fsproj
index 73ba81f..e728483 100644
--- a/AdventOfCode2023.FSharp/AdventOfCode2023.FSharp.Lib/AdventOfCode2023.FSharp.Lib.fsproj
+++ b/AdventOfCode2023.FSharp/AdventOfCode2023.FSharp.Lib/AdventOfCode2023.FSharp.Lib.fsproj
@@ -18,6 +18,7 @@
         <Compile Include="Day6.fs" />
         <Compile Include="Day7.fs" />
         <Compile Include="Day8.fs" />
+        <Compile Include="Day9.fs" />
     </ItemGroup>
 
 </Project>
diff --git a/AdventOfCode2023.FSharp/AdventOfCode2023.FSharp.Lib/Day9.fs b/AdventOfCode2023.FSharp/AdventOfCode2023.FSharp.Lib/Day9.fs
new file mode 100644
index 0000000..81c2855
--- /dev/null
+++ b/AdventOfCode2023.FSharp/AdventOfCode2023.FSharp.Lib/Day9.fs
@@ -0,0 +1,37 @@
+namespace AdventOfCode2023
+
+open System
+open System.Collections.Generic
+
+[<RequireQualifiedAccess>]
+module Day9 =
+
+    let parse (s : string) =
+        use mutable lines = StringSplitEnumerator.make '\n' s
+
+        lines.MoveNext () |> ignore
+
+        let stepsLine = lines.Current.TrimEnd ()
+        let steps = Array.zeroCreate stepsLine.Length
+
+        for i = 0 to stepsLine.Length - 1 do
+            steps.[i] <- (stepsLine.[i] = 'R')
+
+        let dict = Dictionary ()
+
+        while lines.MoveNext () do
+            if not lines.Current.IsEmpty then
+                use mutable line = StringSplitEnumerator.make' ' ' lines.Current
+                line.MoveNext () |> ignore
+        {
+            Steps = steps
+            Nodes = dict
+        }
+
+    let part1 (s : string) =
+        let data = parse s
+        answer
+
+    let part2 (s : string) =
+        let data = parse s
+        0
diff --git a/AdventOfCode2023.FSharp/Test/Test.fsproj b/AdventOfCode2023.FSharp/Test/Test.fsproj
index 9a4c538..b6ff897 100644
--- a/AdventOfCode2023.FSharp/Test/Test.fsproj
+++ b/AdventOfCode2023.FSharp/Test/Test.fsproj
@@ -17,6 +17,7 @@
         <Compile Include="TestDay6.fs" />
         <Compile Include="TestDay7.fs" />
         <Compile Include="TestDay8.fs" />
+        <Compile Include="TestDay9.fs" />
         <EmbeddedResource Include="samples\day1.txt" />
         <EmbeddedResource Include="samples\day1part1.txt" />
         <EmbeddedResource Include="samples\day2.txt" />
diff --git a/AdventOfCode2023.FSharp/Test/TestDay9.fs b/AdventOfCode2023.FSharp/Test/TestDay9.fs
new file mode 100644
index 0000000..ff243f0
--- /dev/null
+++ b/AdventOfCode2023.FSharp/Test/TestDay9.fs
@@ -0,0 +1,49 @@
+namespace AdventOfCode2023.Test
+
+open AdventOfCode2023
+open NUnit.Framework
+open FsUnitTyped
+open System.IO
+
+[<TestFixture>]
+module TestDay9 =
+
+    let sample = Assembly.getEmbeddedResource typeof<Dummy>.Assembly "day9.txt"
+
+    [<Test>]
+    let part1Sample () =
+        sample
+        |> Day9.part1
+        |> shouldEqual 2
+
+    [<Test>]
+    let part2Sample () =
+        Assembly.getEmbeddedResource typeof<Dummy>.Assembly "day9.txt"
+        |> Day9.part2
+        |> shouldEqual 0
+
+    [<Test>]
+    let part1Actual () =
+        let s =
+            try
+                File.ReadAllText (Path.Combine (__SOURCE_DIRECTORY__, "../../inputs/day9.txt"))
+            with
+            | :? DirectoryNotFoundException
+            | :? FileNotFoundException ->
+                Assert.Inconclusive ()
+                failwith "unreachable"
+
+        Day8.part1 s |> shouldEqual 0
+
+    [<Test>]
+    let part2Actual () =
+        let s =
+            try
+                File.ReadAllText (Path.Combine (__SOURCE_DIRECTORY__, "../../inputs/day9.txt"))
+            with
+            | :? DirectoryNotFoundException
+            | :? FileNotFoundException ->
+                Assert.Inconclusive ()
+                failwith "unreachable"
+
+        Day8.part2 s |> shouldEqual 0