#include<iostream>
using namespace std;
int main()
{
	long  long int n;
	cin >> n;

	 int* a = new int[n];

	for (int i = 0; i < n; i++)
	{
		cin >> a[i];
	}
	long long int ans;
	long long int sum = 0;
	long long int end = n - 1;

	for (int i = 0; i < n / 2; i++)
	{
		if (a[i] != a[end])
		{
			ans = a[i] - a[end];
			if (ans < 0)
			{
				ans *= -1;
			}
			a[end] = ans;
			a[i] = ans;
			sum += ans;
		}
		end--;
	}
	cout << sum;

	return 0;
}