public void Visit(TriangleClient client)
{
var(a, b, c) = (client.Figure.A, client.Figure.B, client.Figure.C);
var p = ((double)(a + b + c)) / 2;
client.Area = Math.Sqrt(p * (p - a) * (p - b) * (p - c));
}
public static void Main(string[] args)
{
var s = new Square(10);
var r = new Rectangle(10, 20);
var t = new Triangle(1, 2, 3);
var sc = new SquareClient(s);
var rc = new RectangleClient(r);
var tc = new TriangleClient(t);
var arv = new AreaVisitor();
var anv = new AnglesCountVisitor();
// var dv = new DrawVisitor();
sc.Accept(arv);
rc.Accept(anv);
Console.WriteLine(sc.Area);
Console.WriteLine(rc.AnglesCount);
}