using System;
using System.Collections.Generic;
using System.Text;

namespace euler6
{
    //Find the difference between the sum of the squares 
    //of the first one hundred natural numbers and the square of the sum.
    class Program
    {
        static void Main(string[] args)
        {
            int n =100;

            long squaredSum = (n * (n + 1)) / 2;
            squaredSum *= squaredSum;

            long sumSquares = 0;
            for(int i=1; i<=n;++i)
                sumSquares += (i*i);

            Console.WriteLine(squaredSum - sumSquares);
            Console.ReadLine();
        }
    }
}