Лихва: Rate

using System;

namespace tESt
{
    class Program
    {
        static void Main(string[] args)
        {
            var sum = double.Parse(Console.ReadLine());
            var months = int.Parse(Console.ReadLine());

            double interesSimple = sum;
            double interesComplicated = sum;

            for (int i = 1; i <= months; i++)
            {
                interesSimple = interesSimple + (sum * 0.03);

                interesComplicated = interesComplicated + (interesComplicated * 0.027);
            }

            Console.WriteLine($"Simple interest rate: {interesSimple:f2} lv.");
            Console.WriteLine($"Complex interest rate: {interesComplicated:f2} lv.");

            if (interesSimple < interesComplicated)
            {
                var diff = interesComplicated - interesSimple;
                Console.WriteLine($"Choose a complex interest rate. You will win {diff:f2} lv.");
            }
            else
            {
                var diff =  interesSimple  - interesComplicated;
                Console.WriteLine($"Choose a simple interest rate. You will win {diff:f2} lv.");
            }
        }
    }
}