using System;

public class Program

{

    public void Main()

    {

        double u = 0;

        double r = 0;

        double i = 0;

        double op = 0;

        string op_txt = "";

        Console.WriteLine("U-R-I Rechner");

        Console.WriteLine("U [in V]: (leer wenn gesucht)");

        string U_in = Console.ReadLine();

        Console.WriteLine("R [in Ω]: (leer wenn gesucht)");

        string R_in = Console.ReadLine();

        Console.WriteLine("I [in A]: (leer wenn gesucht)");

        string I_in = Console.ReadLine();

        if(U_in == "" && R_in != "" && I_in != "") {

            r = ConvertInput(R_in);

            i = ConvertInput(I_in);

            op = r * i;

            op_txt = "U = " + op;

        } else if(U_in != "" && R_in == "" && I_in != "") {

            u = ConvertInput(U_in);

            i = ConvertInput(I_in);

            op = u / i;

            op_txt = "R = " + op;

        } else if(U_in != "" && R_in != "" && I_in == "") {

            u = ConvertInput(U_in);

            r = ConvertInput(R_in);

            op = u / r;

            op_txt = "I = " + op;

        } else {

            Console.WriteLine("EINE Variable leer lassen!");

            Console.ReadLine();

        }

        Console.WriteLine(op_txt);

        Console.ReadLine();

    }

    private double ConvertInput(string inp) {

        double int_inp = 0;

        try {

            int_inp = Convert.ToDouble(inp);

        } catch {

            Console.WriteLine("Nur Zahlen eintippen!");

            Console.ReadLine();

        }

        return int_inp;

    }

}