#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 enqeue(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\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;
    }