#include <iostream>
using namespace std;
int main()
{
    int n;   cin >> n;   int arr[n];   long long int sum = 0;
    for ( int i = 0 ; i < n ; i ++ )
    {
        cin >> arr[i];
    }

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

        if ( j + 1 == n/2 )
        {
            cout << sum;
        }
    }

    return 0;
}