import sys input = sys.stdin.readline stack = [] for _ in range(int(input())): commands = input().rstrip().split() if commands[0] == "push": stack.append(int(commands[1])) elif commands[0] == "pop": print(-1) if not stack else print(stack.pop()) elif commands[0] == "size": print(len(stack)) elif commands[0] == "empty": print(0) if stack else print(1) elif commands[0] == "top": print(stack[-1] if..