using System;
public class Program
{
public static void Main()
Console.WriteLine("введите а ");
double a = double.Parse(Console.ReadLine());
Console.WriteLine("введите n ");
double n = double.Parse(Console.ReadLine());
double s = 0;
for (double k = 1; k <= n; k++)
s = s + Math.Pow(a, k);
}
Console.WriteLine("ответ");
Console.WriteLine(s);
Console.ReadKey();