diff --git a/10input.txt b/10input.txt
new file mode 100644
index 0000000..706664b
--- /dev/null
+++ b/10input.txt
@@ -0,0 +1,90 @@
+114
+51
+122
+26
+121
+90
+20
+113
+8
+138
+57
+44
+135
+76
+134
+15
+21
+119
+52
+118
+107
+99
+73
+72
+106
+41
+129
+83
+19
+66
+132
+56
+32
+79
+27
+115
+112
+58
+102
+64
+50
+2
+39
+3
+77
+85
+103
+140
+28
+133
+78
+34
+13
+61
+25
+35
+89
+40
+7
+24
+33
+96
+108
+71
+11
+128
+92
+111
+55
+80
+91
+31
+70
+101
+14
+18
+12
+4
+84
+125
+120
+100
+65
+86
+93
+67
+139
+1
+47
+38
\ No newline at end of file
diff --git a/2020.csproj b/2020.csproj
index 13127c9..a655d06 100644
--- a/2020.csproj
+++ b/2020.csproj
@@ -38,6 +38,9 @@
     <None Update="09input.txt">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </None>
+    <None Update="10input.txt">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </None>
   </ItemGroup>
 
 </Project>
diff --git a/Program.cs b/Program.cs
index 08b9000..82c9a70 100644
--- a/Program.cs
+++ b/Program.cs
@@ -4,6 +4,7 @@
    {
       static void Main(string[] args)
       {
+         var start = System.DateTime.Now;
          Q01.Go();
          Q02.Go();
          Q03.Go();
@@ -13,6 +14,8 @@
          Q07.Go();
          Q08.Go();
          Q09.Go();
+         Q10.Go();
+         System.Diagnostics.Debug.WriteLine($"Total time={(System.DateTime.Now - start).TotalMilliseconds}ms");
       }
    }
 }
diff --git a/Q09.cs b/Q09.cs
index 638e1e1..94afa7c 100644
--- a/Q09.cs
+++ b/Q09.cs
@@ -13,9 +13,17 @@ namespace _2020
 
       public static void Go()
       {
+         var start = DateTime.Now;
          MakeList();
+         Debug.WriteLine($"Q09 MakeList took {(DateTime.Now - start).TotalMilliseconds}ms");
+         var p1start = DateTime.Now;
          Part1();
+         Debug.WriteLine($"Q09 part1 took {(DateTime.Now - p1start).TotalMilliseconds}ms");
+         var p2start = DateTime.Now;
          Part2();
+         Debug.WriteLine($"Q09 part2 took {(DateTime.Now - p2start).TotalMilliseconds}ms");
+
+         Debug.WriteLine($"Q09 took {(DateTime.Now - start).TotalMilliseconds}ms");
       }
 
       static void MakeList()
diff --git a/Q10.cs b/Q10.cs
new file mode 100644
index 0000000..66f2729
--- /dev/null
+++ b/Q10.cs
@@ -0,0 +1,78 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.IO;
+
+namespace _2020
+{
+   class Q10
+   {
+      static List<long> list = new List<long>();
+      static List<long> sortedList = null;
+
+      public static void Go()
+      {
+         var start = DateTime.Now;
+         MakeList();
+         Debug.WriteLine($"Q10 MakeList took {(DateTime.Now - start).TotalMilliseconds}ms");
+         var p1start = DateTime.Now;
+         Part1();
+         Debug.WriteLine($"Q10 part1 took {(DateTime.Now - p1start).TotalMilliseconds}ms");
+         var p2start = DateTime.Now;
+         Part2();
+         Debug.WriteLine($"Q10 part2 took {(DateTime.Now - p2start).TotalMilliseconds}ms");
+
+         Debug.WriteLine($"Q10 took {(DateTime.Now - start).TotalMilliseconds}ms");
+      }
+
+      static void MakeList()
+      {
+         list.Add(0);
+
+         foreach (var line in File.ReadAllLines("10input.txt"))
+         {
+            list.Add(Convert.ToInt64(line));
+         }
+
+         sortedList = new List<long>(list);
+         sortedList.Sort();
+         sortedList.Add(sortedList[^1] + 3);
+      }
+
+      static void Part1()
+      {
+         var diffs = new int[3];
+         for (int i = 1; i < sortedList.Count; i++)
+         {
+            diffs[sortedList[i] - sortedList[i - 1] - 1]++;
+         }
+
+         Debug.WriteLine($"Q10Part1: device joltage={sortedList[^1]}, diffs by 1={diffs[0]}, diffs by 3={diffs[2]}, multiplied={diffs[0] * diffs[2]}");
+      }
+
+      static void Part2()
+      {
+         var pathsToIndices = new List<long>();
+         pathsToIndices.Add(1);
+         for (int i = 1; i < sortedList.Count; i++)
+         {
+            long pathLen = 0;
+            for (int j = i - 1; j >= 0; j--)
+            {
+               if (sortedList[j] + 3 >= sortedList[i])
+               {
+                  pathLen += pathsToIndices[j];
+               }
+               else
+               {
+                  break;
+               }
+            }
+
+            pathsToIndices.Add(pathLen);
+         }
+
+         Debug.WriteLine($"Q10Part2: combinations={pathsToIndices[^1]}");
+      }
+   }
+}