def fibonacci(k): if k == 1 or k == 2: return 1 a, b = 1, 1 for _ in range(2, k): a, b = b, a + b return b try: k = int(input()) if 1 <= k <= 46: result = fibonacci(k) print(result) else: print("输入的 k 应在 1 到 46 之间。") except ValueError: print("输入无效，请输入一个正整数。")