#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<ctype.h>
#define CAPACITY 200
int queue[CAPACITY];
int fornt = 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[fornt]);
    front = (front + 1) % CAPACITY;
    size--;
}
int isVlidNumber(char *s) {
    int len = strlen(s);
    if (len ==0 || len >4)
    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;
}