diff --git a/solvers/UPipeMaze.pas b/solvers/UPipeMaze.pas
index 002184a..1f59dd6 100644
--- a/solvers/UPipeMaze.pas
+++ b/solvers/UPipeMaze.pas
@@ -26,6 +26,10 @@ uses
 
 const
   CStartChar = 'S';
+  CLeftChar = 'l';
+  CRightChar = 'r';
+  CPathChar = '#';
+  CFloodFillChar = '%';
 
 type
   TPointArray = array of TPoint;
@@ -221,8 +225,8 @@ end;
 
 procedure TPipeMaze.CountEnclosureInside;
 begin
-  if not TryCountEnclosureSide('l', FPart2) then
-    TryCountEnclosureSide('r', FPart2);
+  if not TryCountEnclosureSide(CLeftChar, FPart2) then
+    TryCountEnclosureSide(CRightChar, FPart2);
 end;
 
 function TPipeMaze.TryCountEnclosureSide(const AChar: Char; out OCount: Int64): Boolean;
@@ -247,7 +251,7 @@ begin
       if GetEnclosureMapChar(position) = AChar then
       begin
         stack.Push(position);
-        SetEnclosureMapChar(position, '%');
+        SetEnclosureMapChar(position, CFloodFillChar);
         Inc(OCount);
       end;
 
@@ -262,10 +266,10 @@ begin
             // Checks the neighboring position.
             neighbor := position + direction;
             c := GetEnclosureMapChar(neighbor);
-            if (c <> '%') and (c <> '#') then
+            if (c <> CFloodFillChar) and (c <> CPathChar) then
             begin
               stack.Push(neighbor);
-              SetEnclosureMapChar(neighbor, '%');
+              SetEnclosureMapChar(neighbor, CFloodFillChar);
               Inc(OCount);
             end;
           end else
@@ -290,19 +294,19 @@ var
   c: Char;
   i: Integer;
 begin
-  SetEnclosureMapChar(APosition, '#');
+  SetEnclosureMapChar(APosition, CPathChar);
   side := AStepMapping.LeftSide;
-  c := 'l';
+  c := CLeftChar;
   for i := 1 to 2 do
   begin
     for offset in side do
     begin
       sidePosition := APosition + offset;
-      if CheckMapBounds(sidePosition) and (GetEnclosureMapChar(sidePosition) <> '#') then
+      if CheckMapBounds(sidePosition) and (GetEnclosureMapChar(sidePosition) <> CPathChar) then
         SetEnclosureMapChar(sidePosition, c);
     end;
     side := AStepMapping.RightSide;
-    c := 'r';
+    c := CRightChar;
   end;
 end;