vector<string> subsets(size_t n)
{
	if(n == 0){
		vector<string> v1;
		v1.push_back("");
		return v1;
	}

	vector<string> v1 = subsets(n -1);

	vector<string> v2(v1);
	vector<string> v;

	reverse(v2.begin(),v2.end());

	vector<string> :: size_type i = 0;

	for (i = 0;i < v1.size();i++)
	{
		v.push_back("0" + v1[i]);
	}


	for (i = 0;i < v2.size();i++)
	{
		v.push_back("1" + v2[i]);
	}

	return v;