#include <vector>
#include <array>
using namespace std;

template<typename T, template<typename, typename = std::allocator<T>> class U>
struct container
{
	U<T> storage;
};

template<typename T, typename> using arr2 = array<T, 2>;

int main() {
	container<int, vector> a;
	container<double, arr2> b;
}