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

#define MAX_EVENTS 100
#define MAX_CODE_LEN 50

int main() {
    int n;
    if (scanf("%d", &n) != 1 || n < 1 || n > MAX_EVENTS) {
        printf("Invalid input\n");
        return 0;
    }

    char queue[MAX_EVENTS][MAX_CODE_LEN];
    int front = 0, rear = -1, size = 0;

    // Read events
    for (int i = 0; i < n; i++) {
        char event[MAX_CODE_LEN];
        if (scanf("%s", event) != 1) {
            printf("Invalid input\n");
            return 0;
        }

        if (strcmp(event, "-") == 0) {
            // Send next packet
            if (size == 0) {
                printf("the line was empty\n");
            } else {
                printf("%s\n", queue[front]);
                front = (front + 1) % MAX_EVENTS;
                size--;
            }
        } else {
            // Validate packet code (letters and digits only)
            int valid = 1