10845번-큐

#include<bits/stdc++.h>
using namespace std;

int main() {
	ios::sync_with_stdio(0);
	cin.tie(0);
	queue<int> q;
	int n;
	cin >> n;
	while (n--) {
		string s;
		cin >> s;
		if (s == "push") {
			int t;
			cin >> t;
			q.push(t);
		}
		else if (s == "front") {
			if (q.empty()) {
				cout <<  -1 << "\n";
			}
			else cout << q.front()<<"\n";
		}
		else if (s == "back") {
			if (q.empty()) {
				cout << -1 << "\n";
			}
			else cout << q.back() << "\n";
		}
		else if (s == "size")cout << q.size() << "\n";
		else if (s == "pop") {
			if (q.empty()) cout << -1 << "\n";
			else {
				cout << q.front()<<"\n";
				q.pop();
			}
		}
		else {
			if (q.empty())cout << 1 << "\n";
			else cout << 0 << "\n";
		}
	}
}