diff --git a/.common/makefile b/.common/makefile
new file mode 100644
index 0000000..e17e79c
--- /dev/null
+++ b/.common/makefile
@@ -0,0 +1,8 @@
+CXX=clang++
+CXXFLAGS=-std=c++20 -Wall -Wextra
+
+main: format main.cpp
+	$(CXX) $(CXXFLAGS) -g main.cpp -o main
+
+format:
+	clang-format -i -style=google main.cpp
diff --git a/.common/skeleton.cpp b/.common/skeleton.cpp
new file mode 100644
index 0000000..b56858f
--- /dev/null
+++ b/.common/skeleton.cpp
@@ -0,0 +1,14 @@
+#include <iostream>
+
+namespace {
+
+void solve() {
+  // TODO
+}
+
+}  // namespace
+
+int main(void) {
+  solve();
+  return 0;
+}