---

using System;

class Program
{
    static void Main()
    {
        Console.Write("Введите x: ");
        double x = double.Parse(Console.ReadLine());

        Console.Write("Введите a: ");
        double a = double.Parse(Console.ReadLine());

        Console.Write("Введите b: ");
        double b = double.Parse(Console.ReadLine());

        Console.Write("Введите c: ");
        double c = double.Parse(Console.ReadLine());

        double y;

        if (a + b + c > 20)
        {
            y = 2 * x - 1;
        }
        else
        {
            y = 3 * Math.Pow(x, 3) + 1;
        }

        Console.WriteLine("y = " + y);
    }
}