#include<stdio.h>
#inclu**de<stdlib.h>
#include<string.h>
#include<ctype.h>
#define CAPACITY 100
char queue[CAPACITY][50];
int front = 0,rear = 0,size = 0;
void enqueue(char *packet){
    if(size == CAPACITY){
        printf("Invalid input\n");
        exit(0);
    }
    strcpy(queue[rear],packet);
    rear = (rear + 1) % CAPACITY;
    size++;
}
void dequeue(){
    if(size == 0){
        printf("the line was empty\n");
        return;
    }
    printf("%s\n",queue[front]);
    front = (front + 1) % CAPACITY;
    size--;
}
int isValidPacket(char *s){
    if(strcmp(s,"-")==0)return 1;
    for(int i=0;i<strlen(s);i++){
        if(!isalnum(s[i]))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[50];
        if(scanf("%s",token)!=1){
            printf("Invalid input\n");
            return 0;
        }
         if(!isValidPacket(token)){
                printf("Invalid input\n");
                return 0;
            }
            if(strcmp(token,"-") == 0){
            dequeue();
        }else{
            enqueue(token);
        }
    }
    return 0;
}