#include<stdio.h>
#include<ctype.h>
#include<stdlib.h>
#include<string.h>
#define CAPACITY 300
int queue[CAPACITY];
int front =0,rear=0,size=0;
void enqueue(int value)
{
    if(size=CAPACITY)
    {
        printf("Invalid input");
        exit(0);
    }
    queue[rear]=value;
    rear=(rear+1)%CAPACITY;
    size++;
}
void dequeue()
{
    if(size=0)
    {
        printf("The chain was empty");
        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(digit(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("%d",token)!=1)
        {
            printf("Invalid input");
            return 0;
        }
    }
    if(strcmp(token,"-")==0)
    {
        dequeue();
    }
    else
    {
        if(isValidnumber(token))
        {
            printf("Invalid input");
            return 0;
        }
    }
    enqueue(atoi(token));
    }
}
return 0;
}