static void Main(string[] args)
{
Kilogram k1 = new Kilogram(10);
Kilogram k2 = new Kilogram(20);
Kilogram k3 = k1 + k2;
Console.WriteLine(k3);
Gram g4 = new Gram(1000);
Kilogram g5 = (Kilogram)g4; //명시적 형변환
Console.WriteLine(g5);
}
static void Main(string[] args)
{
Kilogram kilo = new Kilogram(5);
Kilogram gram = new Kilogram(10);
Kilogram kilogram = kilo + gram; //연산자 오버로딩 사용
}