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10866
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10866
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import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Deque;
import java.util.LinkedList;
import java.util.Stack;
import java.util.StringTokenizer;
public class Main {
public static void main(String[] args) throws IOException {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
StringBuilder sb = new StringBuilder();
Deque<Integer> que = new LinkedList<>();
int N = Integer.parseInt(br.readLine());
for(int i=0;i<N;i++) {
StringTokenizer st = new StringTokenizer(br.readLine());
String s = st.nextToken();
if(s.equals("push_front")) {
que.addFirst(Integer.parseInt(st.nextToken()));
}
else if(s.equals("push_back")) {
que.addLast(Integer.parseInt(st.nextToken()));
}
else if(s.equals("pop_front")) {
if(que.isEmpty())
sb.append(-1+"\n");
else {
int value = que.pollFirst();
sb.append(value+"\n");
}
}
else if(s.equals("pop_back")) {
if(que.isEmpty())
sb.append(-1+"\n");
else {
int value = que.pollLast();
sb.append(value+"\n");
}
}
else if(s.equals("size")) {
sb.append(que.size()+"\n");
}
else if(s.equals("empty")) {
if(que.isEmpty())
sb.append(1+"\n");
else
sb.append(0+"\n");
}
else if(s.equals("front")) {
if(que.isEmpty())
sb.append(-1+"\n");
else {
sb.append(que.peekFirst()+"\n");
}
}
else {
if(que.isEmpty())
sb.append(-1+"\n");
else {
sb.append(que.peekLast()+"\n");
}
}
}
System.out.println(sb);
}
}