[실4] 28279 - 덱2

#include <iostream>
#include <queue>

using namespace std;

int main()
{
	ios::sync_with_stdio(false);
	cin.tie(NULL);
	cout.tie(NULL);

	int n;
	cin >> n;

	deque<int> dq;

	while(n--)
	{
		int o, t;
		cin >> o;

		if (o == 1)
		{
			cin >> t;
			dq.push_front(t);
		}
		else if (o == 2)
		{
			cin >> t;
			dq.push_back(t);
		}
		else if (o == 3)
		{
			if (dq.empty())
				cout << -1 << "\n";
			
			else
			{
				cout << dq.front() << "\n";
				dq.pop_front();
			}
		}
		else if (o == 4)
		{
			if (dq.empty())
				cout << -1 << "\n";

			else
			{
				cout << dq.back() << "\n";
				dq.pop_back();
			}
		}
		else if (o == 5)
			cout << dq.size() << "\n";

		else if (o == 6)
			cout << dq.empty() << "\n";

		else if (o == 7)
		{
			if (dq.empty())
				cout << -1 << "\n";

			else
				cout << dq.front() << "\n";
		}
		else
		{
			if (dq.empty())
				cout << -1 << "\n";

			else
				cout << dq.back() << "\n";
		}
	}
	return 0;
}