看完这个代码后，不知道错哪了

看完这个代码后，不知道错哪了，求解答，好的答案我会积极采纳，谢谢啦

第一个输出缺少a

class Program
{
    static void Main(string[] args)
    {
        double a = 2.1;
        double b = 3.2;
        int c = 3;
        int d = 3;
        int g = 3;
        int e = 3;
        int f = 3;

        Console.WriteLine("{0}+{1}={2}", a, b, Add(a, b));
        Console.WriteLine("{0}+{1}={2}", c, d, Add(c, d));
        Console.WriteLine("{0}+{1}+{2}={3}", g, e, f, Add(g, e, f));
        Console.ReadKey();
    }
    public static double Add(double a, double b)
    {
        return a + b;
    }
    public static int Add(int c, double d)
    {
        return c + (int)d;
    }
    public static int Add(int g, int e, int f)
    {
        return g + e + f;
    }
}