using System;

using System.Threading;

using System.Threading.Tasks;

​

public class Program

{

    public static void Main()

    {

        long sum = 0;

        Random r = new Random();

        int[] arr = new int[100];

        Parallel.For(0, arr.Length, i =>

        {

            arr[i] = r.Next(10);

        });

        Parallel.For(0, arr.Length, i =>

        {

            Interlocked.Add(ref sum,arr[i]);

        });

        /*long seq_sum=0;

        for(int x=0;x<arr.Length;x++){

        seq_sum+=arr[x];

        }*/

        Console.WriteLine("Sum is "+sum);

        //Console.Write("Seq Sum is "+seq_sum);

    }

}