// editor2
#include<stdio.h>
#include<string.h>
#define max 1000
int dq [max];
int front = -1,rear = -1;
int isEmpty (){
    return(front == 1 || front > rear);
}
void priority_board(int x){
    int (front == -1){
        front = rear = 0;
        dq[front] = x;
    }else{
        front--;
        dq[front] = x;
    }
    }
    void general_board( int x){
        if(rear == -1) {
            front = rear = 0;
            dq[rear] = x;
        }else{
            rear++;
            dq[rear] = x;
        }
    }
    void board_train() {
        if (isEmpty()){
            printf("Invalid operation\n");
            return;
        }
        front++;
    }
    void display(){
        if(isEmpty()){
            printf("No passengers");
            return;
        }
        for (int i = front; i <= rear; i++ )
        printf("%d ",dq[i]);
        printf("\n");
    }
    int main(){
        int N,x;
        char cmd[30];
        scanf("%d",&N);
        while (N--) {
            scanf("%s" , cmd);
            if(strcmp(cmd, "priority_board") == 0) {
                scanf("%d" , &x);
                priority_board(x);
            }
            else if (strcmp(cmd, "general_board") == 0) {
                scanf("%d" , &x);
                general_board(x);
        }
        else if (strcmp(cmd, "general_board") == 0) {
            board_train();
    }
    else if (strcmp(cmd, "display") == 0) {
        display();