#include <bits/stdc++.h>

using namespace std;

#define REP(i,n) for(int i=0; i<(int)(n); i++)

const int INF = 1e6;

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

  int n;
  cin >> n;
  vector<int> a(256);
  REP (i, n) cin >> a[i];

  int sum = accumulate(a.begin(), a.end(), 0);
  int ret = INF;
  vector<int> b(256);
  for (int l = 1; l < 256; l += 2) {
    fill(b.begin(), b.end(), 0);
    b[l/2] = l/2 + 1;
    for (int i = 1; i <= l/2; i++)
      b[l/2-i] = b[l/2+i] = l/2+1-i;
    if ((l+1)*(l+1)/4 > sum)
      break;
    int tmp = 0;
    REP (i, 256) if (a[i] > b[i]) tmp += a[i] - b[i];
    ret = min(ret, tmp);
  }

  cout << ret << endl;
  
  return 0;
}