diff --git a/.common/cpp/skeleton.cpp b/.common/cpp/skeleton.cpp
index 5ce8bb9..da8fc11 100644
--- a/.common/cpp/skeleton.cpp
+++ b/.common/cpp/skeleton.cpp
@@ -59,6 +59,24 @@ inline void answer(const T &ans) {
 inline void yes() { std::cout << "YES\n"; }
 inline void no() { std::cout << "NO\n"; }
 inline void yesno(bool ans) { std::cout << (ans ? "YES" : "NO") << "\n"; }
+#pragma endregion /* output */
+
+#pragma region debug
+void dbg_out() { std::cerr << std::endl; }
+template <typename Head, typename... Tail>
+void dbg_out(Head H, Tail... T) {
+  std::cerr << ' ' << H;
+  dbg_out(T...);
+}
+#ifdef LOCAL
+#define dbg(...)                                                           \
+  std::cerr << '[' << __FILE__ << ':' << __LINE__ << "] (" << #__VA_ARGS__ \
+            << "):",                                                       \
+      dbg_out(__VA_ARGS__)
+#else
+#define dbg(...)
+#endif
+#pragma endregion debug
 
 #pragma region input
 template <typename T>