代码：

#include <iostream>
#include <deque>
using namespace std;

int main() {
    int n;
    cin >> n;
    deque<int> dq;
    for (int i = 0; i < n; i++) {
        int op, x;
        cin >> op;
        switch (op) {
            case 1:
                cin >> x;
                dq.push_front(x);
                break;
            case 2:
                cin >> x;
                dq.push_back(x);
                break;
            case 3:
                dq.pop_front();
                break;
            case 4:
                dq.pop_back();
                break;
            case 5:
                cout << dq.front() << endl;
                break;
            case 6:
                cout << dq.back() << endl;
                break;
        }
    }
    return 0;
}