#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");
        return 0;
    }
    
    for(int i =0 ; i < n ; i++){
        char token[20];
        if(scanf("%s",token) != 1){
            printf("Invalid input");
            return 0;
        }
        
        if(strcmp(token,"-") == 0){
            dequeue();
        }
        else{
            if(!ValidNumber(token)){
                printf("Invalid input");
                return 0;
            }
            enqueue(atoi(token));
        }
    }
    return 0;
}