#include <bits/stdc++.h>

using namespace std;

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);

    int n;
    cin >> n;

    vector<int> a(n);
    for (int i = 0; i < n; ++i)
        cin >> a[i];

    int sum = 0;
    for (int i = 0; i < n / 2; ++i)
        sum += abs(a[n - 1 - i] - a[i]);

    cout << sum;
}