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

#define max 10
int main()
{
    
    int n;
    getchar();
    int deque[max];
    int front=0,rear=0;
    for(int i=0;i<n;i++)
    {
        char command[50];
        fgets(command,sizeof(command),stdin);
        command[strcspn(command,"\n")]='\0';
        if(strncmp(command,"priority_board",14)==0)
        {
        int x;
        scanf(command+15,"%d",&x);
        if(rear-front>=max)
        {
            printf("Invalid operation");
            continue;
        }
        for(int j=rear;j>front;j--)
        {
        deque[j]=deque[j-1];    
        }
        deque[front]=x;
        rear++;
    }
        else if(strncmp(command,"general_board",13)==0)
        {
        int x;
        scanf(command+14,"%d",&x);
        if(rear-front>=max)
        {
            printf("Invalid operation");
            continue;
        }
        deque[rear++]=x;
        }
        else if(strcmp(command,"board_train")==0)
        {
            if(rear==front)
            {
                printf("Invalid operation");
            }
            front++;
        }
        else if(strcmp(command,"display")==0)
        {
            if(rear==front)
            {
                printf("No passengers");
            }
            else{
                for(int j=front;j<rear;j++)
                {
                    printf("%d",deque[j]);
                    if(j<rear-1)
                    printf(" ");
                }
                printf("\n");
            }
            else
            {
                printf("Invalid operation");
            }
        }
        return 0;
    
}