[10845] 큐

#include <iostream>
#include <queue>
#include <string>
using namespace std;
int main()
{
	queue<int> q;
	int i, testcase;
	string str;
	cin >> testcase;
	for (i = 0; i < testcase; i++)
	{
		cin >> str;
		if (str == "push")
		{
			int num;
			cin >> num;
			q.push(num);
		}
		else if (str == "pop")
		{
			if (!q.empty())
			{
				cout << q.front() << endl;
				q.pop();
			}
			else
				cout << "-1\n";
		}
		else if (str == "size")
			cout << q.size() << endl;
		else if (str == "empty")
		{
			if (q.empty())
				cout << "1\n";
			else
				cout << "0\n";
		}
		else if (str == "front")
		{
			if (!q.empty())
				cout << q.front() << endl;
			else
				cout << "-1\n";
		}
		else if (str == "back")
		{
			if (!q.empty())
				cout << q.back() << endl;
			else
				cout << "-1\n";
		}
	}
	return 0;
}