diff --git a/2016/puzzle-13-01.cc b/2016/puzzle-13-01.cc
index bd1443f..8a5391d 100644
--- a/2016/puzzle-13-01.cc
+++ b/2016/puzzle-13-01.cc
@@ -19,9 +19,9 @@ struct Node
     return x_ < rhs.x_ || (x_ == rhs.x_ && y_ < rhs.y_);
   }
 
-  Num x() const noexcept { return x_; }
-  Num y() const noexcept { return y_; }
-  Num cost() const noexcept { return cost_; }
+  constexpr Num y() const noexcept { return y_; }
+  constexpr Num x() const noexcept { return x_; }
+  constexpr Num cost() const noexcept { return cost_; }
 
   Node move_left() { return {x_ - 1, y_, cost_ + 1}; }
   Node move_up() { return {x_, y_ + 1, cost_ + 1}; }
@@ -112,4 +112,4 @@ auto main() -> int
 
   std::cout << "No solution.\n";
   return 1;
-}
\ No newline at end of file
+}
diff --git a/2016/puzzle-13-02.cc b/2016/puzzle-13-02.cc
index 60a4ca8..78955f0 100644
--- a/2016/puzzle-13-02.cc
+++ b/2016/puzzle-13-02.cc
@@ -19,9 +19,9 @@ struct Node
     return x_ < rhs.x_ || (x_ == rhs.x_ && y_ < rhs.y_);
   }
 
-  Num x() const noexcept { return x_; }
-  Num y() const noexcept { return y_; }
-  Num cost() const noexcept { return cost_; }
+  constexpr Num x() const noexcept { return x_; }
+  constexpr Num y() const noexcept { return y_; }
+  constexpr Num cost() const noexcept { return cost_; }
 
   Node move_left() { return {x_ - 1, y_, cost_ + 1}; }
   Node move_up() { return {x_, y_ + 1, cost_ + 1}; }
@@ -112,4 +112,4 @@ auto main() -> int
 
   std::cout << "Number of visited locations: " << visited.size() << '\n';
   return 0;
-}
\ No newline at end of file
+}