diff --git a/18input.txt b/18input.txt
new file mode 100644
index 0000000..3a62272
--- /dev/null
+++ b/18input.txt
@@ -0,0 +1,371 @@
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+2 * ((7 * 9 * 3) * 7 * 6) * 8 * 3
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+((8 + 9 + 8 + 3 * 4) * 9 * (3 * 6 + 5) * 6 + (2 * 3 * 4 + 9)) + 5 + 2 + (4 + (7 * 8 + 4 + 4 * 7 + 8)) * 5 + 4
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+2 * (9 + 9) * 9 * 9
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+(6 + 6 * 9 + 3) + (4 + 9 * 2 + 9 * 2 * 9) + 7
+(6 * 6) * 7 + 9 * 2 * 2 * (4 + (8 + 7 + 9 + 7 + 4 * 2) + 6 * 4 + 8 * 5)
+((9 * 7 * 9) + 6 + 4) * (6 * (3 + 5) + 6 * 5) + 6 + 3 * 2
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+9 * 9 * 6 * ((6 + 9 + 7) * 5 + 9 + (9 + 4 * 7)) * 6
+(3 + 9) + ((9 + 3 + 9 + 9) * 6 + (2 * 6 + 8 * 2 + 2)) + 3 * 3 * 9 + 3
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+4 + 6 * (7 + (6 * 5) * (5 * 2 * 9 + 4) + 2) * 9
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+(2 + 9) * (8 * 4 * 5) * 9
+(4 + 6 + 5 * 7 + (5 * 4 + 2 * 2 + 9 + 2)) + 4 + 8 * 3 + 3
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+2 + (3 + 9) * 7 + 6 * 7
+2 * 5 * 9 * (2 + (5 * 8 * 4 * 4 + 8 + 7) + 3 * (5 + 4 * 8 + 5 * 9 + 7))
+((4 + 5 + 7 + 4 * 3) + (9 + 7 + 5 + 7 + 5) + 8 * 9 + 7) * 6 + 4 * (6 + 3 + (6 + 7)) * 8
+9 + 3 + (8 + 4 * (8 + 3) * 8 * 8) * (8 * 2 * 9) * 5
+(8 * (3 + 2 * 7 + 2 + 6) + 9 + 2 * 9) + 3 * 5
+6 + 6 * 2 * 8 * 5 + 4
+(6 + (7 + 2 * 6 + 3) + (3 + 7 * 5 * 6 + 4 + 9) * 5 * 3) * 4 * (6 + 3 * 2 + 4 * (9 + 6))
+2 * ((7 * 6 * 3 + 9 + 9 + 9) * 2 + 9 * 8)
+9 * (3 * 6 + (9 * 9 + 7 * 9) + 8) + 8 + 6 + 4
+4 + 4 * (4 * 8 + 4 * 2 * 2 + 3) * 3 + 6 + 9
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+5 + 3 * ((2 * 7 + 9 * 2) * 3) * 6 * 6 + 8
+(6 + 3 + (2 + 7 + 4) + 4) * 4 * 4 * (9 * 2 * 7 * (9 + 3 + 8 + 5) * 3) + 8
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+(9 + (3 + 7 + 9 * 2 * 8) + 3 * 5 * 7 * 2) * 6 + 8 * 7 + (5 + 7 + 4 * 5 * 4)
+8 * 2 + ((5 + 9) + 2 + 8 + (8 * 2) * 3 + 8) * 9 + (2 + 8 * (8 + 4 + 7 * 9) * 4 + 7 + 6)
+((8 * 8 + 7 * 7 + 3) * 8 * (4 + 8 * 4 + 4 + 4 + 4)) + 9 * 2 + 8
+5 * (6 * 3 + 4 * 2 + 7 * 5) * (3 * 7 * 8 * 3 + 3 + 6) + 6 + 4 + ((4 * 6 + 3 * 8 + 4 + 5) + (3 * 5 + 8) + 6)
+6 + (9 * (5 * 2 + 9 + 6 * 2 + 2) + (4 + 3 + 6 + 5) * 2 + 5)
+4 + ((3 + 2 * 6 * 3) * 5 + 8 * (5 * 7 * 4 + 7 * 6 + 6) + 3 + 7) + 9 + 8 * 5
+7 * (5 * 5 + 5 * (7 + 6 + 6 + 5 + 2 + 6) + 6) + 7 * 8
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+(8 + 9 + (7 * 7 * 5 + 6) * 4 + (5 * 5 * 4) + 5) * 6 + 8 * 6 * 9 * 9
+4 * ((5 * 4) + 7) + 2
+2 + (3 * 5 + 7)
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+8 + 2 * 6 * 5 + 8 * (2 + 9 * 7)
+(5 + 4 * 5 * 5 * 5) * 6 + ((9 + 9) * 7 + 6 + 7) + 5 * 8 * 7
+4 + (4 * (9 + 3 + 8) + 4 + (9 * 6 * 2) + 8) * 2
+(4 * 6 + 5 * 8 * 9 * 7) * 8 * 7 * ((8 + 6 * 7 + 4 * 9 * 3) + 7)
+9 + 5 * 2 * ((7 * 9) + 4 * 4)
+5 * 5 * (4 * 8 + (5 + 8) + 9 * 6 * 5)
+7 + (7 * 2) + (4 + 7 * 5 * 5 * 4)
+6 + 4 + 2 + 8 * (6 + 3 * 7 * (5 * 2 * 2 + 5)) + (7 * 9 * 4 + (2 + 5 + 3 + 5) + 9 * 9)
+(4 * 2 + 9 * 7 * 3) * (5 * 4 * 2 * 4 * (9 + 4)) * 2
+((4 + 6 + 5) * 2) + 8 * (7 + 9 + 3 * 8) * 3 * 4
+4 * (9 + 4 * 8) + 2 * 4 + 9
+4 + (4 + 5) + 5 * 3 + 9 * 8
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+((9 * 8 * 7) * 3 * (5 + 6 * 7 + 4) + 9 + 7 + 4) * 9 * (7 * 3 * 8 * 7 * 4) * 7 * 2
+(2 * 5 * (8 + 2) + (2 * 3 * 7 + 6 + 9) + 6 * 3) + 5 * 2 * 5
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+3 + ((4 * 6 + 4) * 4 * (9 * 3 + 5 + 7 * 3) + 3) * 6 * 9 + 9
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+((3 + 9 * 2 + 7 * 8) * 4 + 3) + (9 + 9 + 5 * (3 * 5 + 7) + 8 + 9)
+4 + (3 + 4 + 4 * 8 * 6 * 5) * (7 * 5 * 9 + 7 + 8)
+(8 * (3 * 8 + 4 * 4 + 4)) + 7 * 9
+(2 * 2 + 9) * 5 + (8 + 3 * 3 + 2) + 7
+2 + 7
+5 + (3 * 2 * 5 + 4) * (5 * 4 * 9 + 5) * 8 * 6 * 4
+8 * 7 * 6 + (2 * 7 * (8 + 2 * 3 * 5) * 5) + 6
+8 * 5 * (2 * 2 * 6) * 3 + 7 + 9
+((4 + 4 + 9) * 5) * (6 * (6 + 3)) + 2 * (7 * 6 + 3)
+(6 * (3 * 9 * 4) + 6 * 5 + 5 + 7) * (7 * 5) * 2 * 2 * (5 + 5) * 4
+3 + 7 * (3 + 9)
+(9 * 2 * (4 * 6)) + 9
+((3 * 6 + 5 * 6 + 9 + 6) * 9 + 9) * 5 + 3 + 4
+(8 + (5 * 7 * 2 + 2) + 9 * 6 * 9) * 4 + 4 * 9 + 8 * 5
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+(9 + 5) + 8 + (5 * 8 + 5 * 2 + 8) + 2
+2 * (2 * 5) * (8 + 8 * (2 * 5 + 9 + 9) + 5 * 8 + 2) + 6 * 9
+(6 * (4 * 5) + (4 * 5 + 3 * 7 * 2 + 4)) * 2 * 8 * 2
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+3 + 7 + (8 * 5 + 7 * 6)
+9 + 5 * 8 + (6 * (2 + 9) * 7 + 7 + 8) + 6
+9 * 4 * (5 * (6 * 6)) + 7 * (6 + 7 + 5 * 3 * 9 + 4)
+5 + 9 * 7 * (6 + 2)
+8 + (9 + 6 * 5 * (6 + 9) * 5) * (3 + 6 + 8)
+2 + (7 * 4 * (9 * 4 * 5 * 2)) + (8 + 2) * 4 * (3 + 8)
+(5 * 8 * (2 + 7 * 2) * (6 + 4 * 9 * 8 + 3 + 2) * 7) * 8
+(8 * (5 * 2 + 5 * 4 + 4) + 8) * 4 * 4 * (6 + 6) + 7 + 9
+(7 * 2 + 2 + 9 + 7) * ((6 + 5) * 3) + (2 * 4 + (8 * 7 * 9 * 7) + 5 + 6 * 9) + 3 + 4 + 2
+5 + 7 + 4
+4 + 8 * 6 * (9 + 4 * 6 + (9 * 8) + 5)
+4 + 9 * 2
+2 + (7 * 7 * 2 + 2 * 3 + (6 + 9 * 7 * 4)) + 5 * 4
+(5 + 9 * 9) * 3 * 2 + 5 + 6
+(3 * 6 + 5 + 8) * 9 + 9 * 7 * 3 + 7
+((7 * 5 + 9 + 8 * 8) * 5 * 2 * 7) + (2 + 8 + 5) * 3
\ No newline at end of file
diff --git a/2020.csproj b/2020.csproj
index 590b5b5..ddb8a35 100644
--- a/2020.csproj
+++ b/2020.csproj
@@ -56,6 +56,9 @@
     <None Update="15input.txt">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </None>
+    <None Update="18input.txt">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </None>
   </ItemGroup>
 
 </Project>
diff --git a/Program.cs b/Program.cs
index c57c53e..315b98f 100644
--- a/Program.cs
+++ b/Program.cs
@@ -20,6 +20,7 @@
          Q13.Go();
          Q14.Go();
          Q15.Go();
+         Q18.Go();
          Util.Log($"Total time={(System.DateTime.Now - start).TotalMilliseconds}ms");
       }
    }
diff --git a/Q18.cs b/Q18.cs
new file mode 100644
index 0000000..608d159
--- /dev/null
+++ b/Q18.cs
@@ -0,0 +1,176 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+
+namespace _2020
+{
+   class Q18
+   {
+      static List<string> list = new List<string>();
+
+      public static void Go()
+      {
+         var start = DateTime.Now;
+         MakeList();
+         Util.Log($"Q18 MakeList took {(DateTime.Now - start).TotalMilliseconds}ms");
+         var p1start = DateTime.Now;
+         Part1();
+         Util.Log($"Q18 part1 took {(DateTime.Now - p1start).TotalMilliseconds}ms");
+         var p2start = DateTime.Now;
+         Part2();
+         Util.Log($"Q18 part2 took {(DateTime.Now - p2start).TotalMilliseconds}ms");
+
+         Util.Log($"Q18 took {(DateTime.Now - start).TotalMilliseconds}ms");
+      }
+
+      static void MakeList()
+      {
+         list = new List<string>(File.ReadAllLines("18input.txt"));
+      }
+
+      static long DoOp(long left, long right, char op)
+      {
+         switch (op)
+         {
+            case '+':
+               return left + right;
+
+            case '*':
+               return left * right;
+
+            default:
+               throw new Exception("unrecognized op");
+         }
+      }
+
+      static void Part1()
+      {
+         long sum = 0;
+         for (int i = 0; i < list.Count; i++)
+         {
+            var evals = new Stack<long>();
+            var ops = new Stack<char>();
+            long currVal = 0;
+            char currOp = '+';
+
+            foreach (var ch in list[i])
+            {
+               if (ch == ' ')
+               {
+                  continue;
+               }
+               else if (ch == '+' || ch == '*')
+               {
+                  currOp = ch;
+               }
+               else if (ch == '(')
+               {
+                  ops.Push(currOp);
+                  evals.Push(currVal);
+                  currVal = 0;
+                  currOp = '+';
+               }
+               else if (ch == ')')
+               {
+                  var lastOp = ops.Pop();
+                  var lastVal = evals.Pop();
+                  currVal = DoOp(currVal, lastVal, lastOp);
+               }
+               else
+               {
+                  var val = ch - '0';
+                  currVal = DoOp(currVal, val, currOp);
+               }
+            }
+
+            sum += currVal;
+         }
+
+         Util.Log($"Q18Part1: sum={sum}");
+      }
+
+      static long SolveAddPrecedence(string exp)
+      {
+         var evals = new Stack<long>();
+         var ops = new Stack<char>();
+         long currVal = 0;
+         char currOp = '+';
+         var numStr = "";
+
+         foreach (var ch in exp)
+         {
+            if (ch == ' ')
+            {
+               if (!string.IsNullOrEmpty(numStr))
+               {
+                  currVal = DoOp(currVal, Convert.ToInt32(numStr), currOp);
+                  numStr = "";
+               }
+               continue;
+            }
+            else if (ch == '+' || ch == '*')
+            {
+               currOp = ch;
+               if (ch == '*')
+               {
+                  ops.Push(currOp);
+                  evals.Push(currVal);
+                  currVal = 0;
+                  currOp = '+';
+               }
+            }
+            else
+            {
+               numStr += ch;
+            }
+         }
+
+         if (!string.IsNullOrEmpty(numStr))
+         {
+            currVal = DoOp(currVal, Convert.ToInt32(numStr), currOp);
+         }
+
+         return currVal;
+      }
+
+      static void Part2()
+      {
+         long sum = 0;
+         for (int i = 0; i < list.Count; i++)
+         {
+            long currVal = 0;
+
+            var expressions = new Stack<string>();
+            string currExp = "";
+
+            foreach (var ch in list[i])
+            {
+               if (ch == '(')
+               {
+                  expressions.Push(currExp);
+                  currExp = "";
+               }
+               else if (ch == ')')
+               {
+                  var subVal = SolveAddPrecedence(currExp);
+                  currExp = expressions.Pop();
+                  currExp += subVal;
+               }
+               else
+               {
+                  currExp += ch;
+               }
+            }
+
+            if (!string.IsNullOrEmpty(currExp))
+            {
+               currVal = SolveAddPrecedence(currExp);
+            }
+
+            sum += currVal;
+         }
+
+         Util.Log($"Q18Part2: sum={sum}");
+      }
+   }
+}