def lantern_chain():
    try:
        n = int(input().strip())
        if not (1 <= n <= 100):
            print("Invalid input")
            return
        commands = input().strip().split()
        if len(commands) != n:
            print("Invalid input")
            return
        
        capacity = n  # max possible elements
        queue = [0] * capacity
        front = 0
        rear = -1
        size = 0
        
        for cmd in commands:
            if cmd == "-":  # removal
                if size == 0:
                    print("the chain was empty")
                else:
                    print(queue[front])
                    front = (front + 1) % capacity
                    size -= 1
            else:  # addition
                try:
                    color = int(cmd.lstrip("0") or "0")  # remove leading zeros
                    if not (1 <= color <= 1000):
                        print("Invalid input")
                        return
                except:
                    print("Invalid input")
                    return
                
                if size == capacity:
                    print("Invalid input")  # queue overflow
                    return
                
                rear = (rear + 1) % capacity
                queue[rear] = color
                size += 1
                
    except:
        print("Invalid input")

# Run the function
lantern_chain()