#include <bits/stdc++.h>
using namespace std;

#define int long long
#define rep(i,l,r) for(int i=(int)(l);i<(int)(r);i++)
#define all(x) (x).begin(),(x).end()
#define sz(x) ((int)x.size())
template<class T>bool chmax(T &a,T b){if(a<b){a=b;return 1;}return 0;}
template<class T>bool chmin(T &a,T b){if(a>b){a=b;return 1;}return 0;}

typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<vi> vvi;

const int inf = 1LL<<60;
const int mod = 1e9 + 7;
const double eps = 1e-9;

/*{
  }*/

signed main(){
  int n;
  cin >> n;

  vi a(101);
  rep(i, 1, n+1) cin >> a[i];

  int ans = inf;
  rep(c, 1, 101) rep(h, 1, min(c, 101-c)+1){
    int rem = 0, mov = 0;
    rep(i, 1, 101){
      if(c-h < i and i < c+h){
        int need = h - abs(c-i);
        if(a[i] < need){
          mov += need - a[i];
        }else{
          rem += a[i] - need;
        }
      }else{
        rem += a[i];
      }
    }

//    cout << c << " " << h << ": " << rem << " " << mov << endl;

    if(rem < mov) continue;
    chmin(ans, rem);
  }

  cout << ans << endl;

  return 0;
}