完成 switch 语句，并在末尾添加正确的关键字，以指定在 switch 语句中没有 case 匹配时要运行的代码。
int day = 4; switch (@(3)) { @(4) 1: cout << "Saturday"; break; @(4) 2: cout << "Sunday"; @(5); @(7): cout << "Weekend"; }
int day = 4; switch (day) { case 1: cout << "Saturday"; break; case 2: cout << "Sunday"; break; default: cout << "Weekend"; }