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

int deque[1000], front = 0, rear =-1,count = 0;

int main(){
    int n,x;
    char op[20];
    scanf("%d ",&n);
    while(n--){
        scanf("%s",op);
        if(strcmp(op, "join_front")==0){
            front("%d" ,&x);
            front = (front-1 + 1000) % 1000;
            deque[front] = x;
            count++;
        }else if(strcmp(op, "join_rear")==0{
            rear=(rear + 1) % 1000;
            scanf("%d", &x);
            deque[rear] =x;
            count++;
        }else if(strcmp(op, "issue") == 0{
            if(count == 0)printf("Invalid operation\n");
            else( front = (front +1)%1000;
            count--;
        }else if(strcmp(op, "display") == 0){
            if(count == 0) printf("No VIPs in queue\n")
             else{
                for(int i=0; i<count; i++)
                printf("%d ",deque[(front + i) % 1000]);
                printf("\n");
             }
        }
    }
    return 0;
}