#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#define CAPACITY 200 
int queue[CAPACITY];
int front = 0; rear = 0; size = 0;
void enqueue(int value) {
    if (size == CAPACITY) {
        printf("Invalid input\n");
        exit(0);
    }
    queue[rear] = value;
    rear = (rear + 1) % CAPACITY;
    size++;
}
void dequeue() {
    if (size == 0) {
        printf("the chain was empty\n");
        return;
    }
    printf("%d\n",queue[front]);
    front = (front + 1) % CAPACITY;
    size--;
}
int isValidNumber(char *s) {
    int len = strlen(s);
    if (len == 0 || len > 4)
    return 0;
    for (int i = 0; i < len; i++) {
        if (!isdigit(s[i]))
        return 0;
    }
    int val = atoi(s);
    if (val < 1 || val > 1000)
    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[20];
        if (scanf("%s", token) !=1) {
            printf("Invalid input\n");
            return 0;
        }
        if (strcmp(token, "-") == 0) {
            dequeue();
        } else {
            if (!isValidNumber(token)) {
                printf ("Invalid input\n");
                return 0;
            }
            enqueue(atoi(token));
        }
    }
    return 0;
}