#include<stdio.h>
#include<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, "-")== 0) return 1;
    for (int i = 0; i < strlen(s); i++) {
        if (!isalum(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++) {
        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;
}