#include<stdio.h>
#include<string.h>

#define MAX 100

int main(){
    int n;
    scanf("%d",&n);
    int deque[MAX];
    int front = 0, rear = -1,size = 0;
    char command[20];
    int x;
    while(1){
        scanf("%s",command);
    }
    for(int i=0;i<n;i++){
        scanf("%s",command);
        if(strcmp(command,"join_front") == 0){
            scanf("%d",&x);
            if(size == 0){
                deque[0] = x;
                front = 0;
                rear = 0;
            }else{
                for(int j=rear+1;j>front;j--){
                    deque[j] = deque[j-1];
                }
                deque[front] = x;
                rear++;
            }
            size++;
        }
        else if(strcmp(command,"join_rear") == 0){
            scanf("%d",&x);
            rear++;
            deque[rear] = x;
            size++;
        }
        else if(strcmp(command,"issue") == 0){
            if(size == 0){
                printf("Invalid operation\n");
            }else{
                front++;
                size--;
            }
        }
    else if(strcmp(command,"display") == 0){
        if(size == 0){
            printf("No VIPs in queue\n");
        }else{
            for(int j=front;j<= rear;j++){
                printf("%d",deque[j]);
                if(j<rear)printf(" ");
            }
            printf("\n");
        }
    }
    }
        return 0;
    }