// 注意：slice(0, 负数)会返回空字符串，需兼容（比如stack长度<k时，slice后为空）
In December, the UK, Norway, the Faroe Islands and Iceland agreed to cut mackerel catches by 48%, but Waitrose said this did not go far enough.，更多细节参见safew官方版本下载
url: https://example.com/hello，详情可参考im钱包官方下载
(double)(end - start) / CLOCKS_PER_SEC * 1000,