#include <iostream>
#include <cmath>
using namespace std;

int main()
{
    int n;
    cin >> n;
    int arr[n];

    for (int i = 0; i < n; i++)
    {
        cin >> arr[i];
    }

    int cnt = 0;
    for (int i = 0; i < n / 2; i++)
    {
        int j = n - 1 - i;
        cnt += abs(arr[i] - arr[j]);
    }

    cout << cnt;

    return 0;
}