#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<ctype.h>
#define CAPACITY 100
char queue[CAPACITY][50];
int front = 0, rear = 0, size = 0;
void enqueue(char *packet) {
    if (size == CAPACITY){
        printf("Invalid input\n");
        rear = (rear + 1) % CAPACITY;
        size++;
    }
    void dequeue() {
        if (size == 0) {
            printf("the line was empty\n");
            return;
        }
        printf("%s\n", queue[front]);
        front = (front + 1) % CAPACITY;
        size--;
    }
    int isValidPacket(char *s) {
        if (strcmp(s,"-") == 0) return 1;
        for (int i = 0; i < strlen(s); i++) {
            if (!islnum(s[i])) return 0;
        }
        return 1;
    }
    int main() {
        int n;
        if (scanf("%d" , &n)!=1 || n <1 || n > 100) {
            printf("Invalid input\n");
            return 0 ;
        }
        for (int i = 0; i < n; i++) {
            char token[50];
            if (scanf("%s", token) !=1){
                printf("Invalid input\n");
                return 0;
            }
            if (!isValidPacket(token)) {
                printf("Invalid input\n");
                return 0;
            }
            if (strcmp(token,"-") == 0) {
                dequeue();
            } else {
                enqueue(token);
            }
        }
        return 0;
    }