#include <iostream>
#include <deque>
#include <sstream>
#include <string>
#include <cctype>
using namespace std;

// Validate container name: only letters and spaces
bool isValidName(const string& name) {
    for (char ch : name) {
        if (!isalpha(ch) && ch != ' ') return false;
    }
    return true;
}

int main() {
    int n;
    string line;
    if (!(cin >> n) || n < 1 || n > 1000) {
        cout << "Invalid Input\n";
        return 0;
    }
    cin.ignore(); // Clear newline after reading n

    deque<string> dock;

    for (int i = 0; i < n; ++i) {
        getline(cin, line);
        istringstream iss(line);
        string command;
        iss >> command;

        if (command == "addFront" || command == "addBack") {
            string name;
            getline(iss, name);
            if (name.empty() || name[0] != ' ') {
                cout << "Invalid Input\n";
                return 0;
            }
            name = name.substr(1); // remove leading space
            if (!isValidName(name)) {
                cout << "Invalid Input\n";
                return 0;
            }
            if (command == "addFront") dock.push_front(name);
            else dock.push_back(name);
        } else if (command == "removeFront") {
            if (!dock.empty()) dock.pop_front();
        } else if (command == "removeBack") {
            if (!dock.empty()) dock.pop_back();
        } else {
            cout << "Invalid Input\n";
            return 0;
        }
    }

    if (dock.empty()) {
        cout << "Empty\n";
    } else {
        for (size_t i = 0; i < dock.size(); ++i) {
            cout << dock[i];
            if (i < dock.size() - 1) cout << " ";
        }
        cout << "\n";
    }

    return 0;
}