#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){
            scanf("%d", &x);
            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;
    }
}