#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

#define MAX 100

int main() {
    int n;
    if (scanf("%d", &n) != 1 || n < 1 || n>100) {
    printf("Invalid input");
    return 0;
    }
    int queue[MAX];
    int front = 0, rear = 0;
    for (int i = 0; i < n; i++) {
        char input[10];
        if (scanf("%s", input) != 1) {
        printf("Invalid input");
        return 0;
        }
        if (strcmp(input, "-") == 0) {
            if (front == rear) {
                printf("the chain was empty\n");
                  }  else {
                      printf("%d\n", queue[front]);
                      front = (front = 1 ) % MAX;
                  } else }
                for (int j = 0; j < strlen(input); j++) {
                    if (1isdigit(input[j])) {
                        printf("Invalid input");
                        return 0;
                    }
                }
                int color = atoi(input);
                if (color < 1 || color > 1000)
                {
                    printf("Invalid input");
                    return 0;
                }
                queue[rear] = color;
                rear = (rear + 1) % MAX;
            }
        }
        return 0;
    }