#include<stdio.h>
#include<stdlib>
#define MAX_CAPACITY 101
int lanternchain[MAX_CAPACITY];
int front=0;
int rear=-1;
int size=0;
int capacity;
void addLantern(int colorCode)
{
    if(size<capacity)
    {
        rear=(rear+1)%capacity;
        lanternChain[rear]=colorCode;
        size++;
    }
}
int removeLantern()
{
    if(size>0)
    {
        int removeColor=lanternChain[front];
        front=(front+1)%capacity;
        size--;
        return removeColor;
    }
    return -1;
}
int isEmpty()
{
    return(size==0)
}
int main()
{
    int n;
    if(scanf("%d",&n)!=1)
    {
        printf("Invalid input");
        return 0;
    }
    if(n<1||n>100)
    {
        printf("Invalid input");
        return 0;
    }
    capacity=n+1;
    for(int i=0;i<n;i++)
    {
        char operation[10];
        if(scanf("%s",operation)!=1)
        {
            printf("Invalid input\n");
            return 0;
        }
        if(operation=='-')
        {
            if(isEmpty())
            {
                printf("the chain was empty");
            }
            else
            {
                int removeColor=removeLantern();
                printf("%d\n",removedColor);
            }
        }
        else
        {
            
            int colorCode=atoi(operation);
            if(colorCode<1||colorCode>1000)
            {
                printf("Invalid input");
                return 0;
            }
            addLantern(colorCode);
        }
    }
    return 0;
}