diff --git a/.common/cpp/skeleton.cpp b/.common/cpp/skeleton.cpp
index 8202982..5ce8bb9 100644
--- a/.common/cpp/skeleton.cpp
+++ b/.common/cpp/skeleton.cpp
@@ -39,6 +39,17 @@ std::ostream &operator<<(std::ostream &os, std::pair<T, U> const &p) {
   return os << p.first << " " << p.second;
 }
 
+template <typename C, typename T = typename std::enable_if<
+                          !std::is_same<C, std::string>::value,
+                          typename C::value_type>::type>
+std::ostream &operator<<(std::ostream &os, const C &v) {
+  std::string sep;
+  for (const T &x : v) {
+    os << sep << x, sep = " ";
+  }
+
+  return os;
+}
 
 template <typename T>
 inline void answer(const T &ans) {