#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define MAX 100
int deque[MAX];
int front = -1, rear = -1;
int isEmpty(){
    return (front == -1);
}
void joinfront(int x){
    if(front == 0 && rear == MAX-1){
        printf("Queue is full\n");
        return;
    }
    if(front == -1){
        front = rear = 0;
    }
    else if(front > 0){
        front--;
    }
    else{
        for(int i = rear; i >= front; i--)
        deque[i + 1] = deque[i];
        rear++;
    }
    deque[front] = x;
}
void joinrear(int x){
    if(rear == MAX - 1){
        printf("Queue is full\n");
        return;
    }
    if(front == -1){
        front = rear = 0;
    }
    else{
        rear++;
    }
    deque[rear] = x;
}
void issue(){
    if(isEmpty()){
        printf("Invalid operation\n");
        return;
    }
    front++;
    if(front > rear)
    front = rear = -1;
}
void display(){
    if(isEmpty()){
        printf("No VIPs in queue\n");
        return;
    }
    for(int i = front; i <= rear; i++){
        printf("%d", deque[i]);
        if(i < rear) printf(" ");
    }
    printf("\n");
}
int main(){
    int n;
    scanf("%d", &n);
    for(int i = 0; i < n; i++){
        char cmd[20];
        scanf("%s", cmd);
        if(strcmp(cmd,"join_front") == 0){
            int x;
            scanf("%d", &x);
            joinFront(x);
        }
        else if(strcmp(cmd,"join_rear") == 0){
            int x;
            scanf("%d", &x);
            joinRear(x);
        }
        else if(strcmp(cmd,"issue") == 0){
            issue();
        }
        else if(strcmp(cmd,"display") == 0){
            display();
        }
        else{
            printf("Invalid operation\n");
            return 0;
        }
    }
    return 0;
}