#include <bits/stdc++.h>
using namespace std;
#define int long long   // <-----!!!!!!!!!!!!!!!!!!!

#define rep(i,n) for (int i=0;i<(n);i++)
#define rep2(i,a,b) for (int i=(a);i<(b);i++)
#define rrep(i,n) for (int i=(n)-1;i>=0;i--)
#define rrep2(i,a,b) for (int i=(b)-1;i>=(a);i--)
#define all(a) (a).begin(),(a).end()

typedef long long ll;
typedef pair<int, int> P;

const int WIDTH = 1000;
const int TOP = 105;

int sumBlock(int t) {
    return t * t;
}

signed main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(0);

    int N;
    cin >> N;
    vector<int> a(WIDTH, 0);
    int sum_a = 0;
    rep(i, N) {
        cin >> a[i];
        sum_a += a[i];
    }

    int ans = 99999999;
    rep2(t, 1, TOP) {
        if (sumBlock(t) > sum_a) break;
        int cnt = sum_a - sumBlock(t); // 捨てる分
        rep(i, t) {
            // 足りない分を移動回数に足す
            cnt += max(0ll, (i + 1) - a[i]);
            // 鏡写しの反対側
            if (i != t - 1) cnt += max(0ll, (i + 1) - a[2 * (t - 1) - i]);
        }
        ans = min(ans, cnt);
    }

    cout << ans << endl;

}