实现代码

private static int Calu(int number){    var sum = 0;    if (number % 2 == 0)        sum = -(number / 2);    else        sum = -(number - 1) / 2 + number;    return sum;}

代码调用

private static void Main(string[] args){    Console.WriteLine(Calu(1));    Console.WriteLine(Calu(2));    Console.WriteLine(Calu(3));    Console.WriteLine(Calu(4));    Console.WriteLine(Calu(5));    Console.WriteLine(Calu(6));    Console.ReadLine();}

运行效果