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using System;
using System.Threading.Tasks.Dataflow;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            double s = 0;
            int x = 1;
            for (int i = 1; i < 10; i++)
            {
                s += Math.Cos(i * x) / Math.Pow(x, i + 1);
            }
            Console.WriteLine(s);
        }
    }
}

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