#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <cmath>
#include <string>
#include <vector>
#include <algorithm>
#include <queue>
#include <map>
#include <functional>
#include <set>
#include <numeric>
#include <stack>
#include <utility>
#include <time.h>
//#include "util.h"

using namespace std;
typedef long long ll;
typedef unsigned long long ull;

#define PI 3.14159265358979323846
#define EPS 1e-6
#define MIN(a,b) ((a)<(b)?(a):(b))
#define MAX(a,b) ((a)>(b)?(a):(b))
#define CHAR_BIT 8

template <typename _Ty>
ostream& operator << (ostream& ostr, const vector<_Ty>& v) {
	if (v.empty()) {
		cout << "{ }";
		return ostr;
	}
	cout << "{" << v.front();
	for (auto itr = ++v.begin(); itr != v.end(); itr++) {
		cout << ", " << *itr;
	}
	cout << "}";
	return ostr;
}

int yuki0077()
{
	int N, s = 0, h;
	vector<int> A(512, 0);

	cin >> N;
	for (int i = 0; i < N; i++) {
		cin >> A[i];
		s += A[i];
	}

	for (h = 0; h * h <= s; h++); h--;

	int minMove = 100000;
	// pos : ピラミッドの左端
	for (int pos = 0; pos < N; pos++) {
		// move : 移動回数, B : 差分
		vector<int> B = A;
		for (int i = 1; i <= h; i++)
			B[pos + i - 1] = max(0, B[pos + i - 1] - i);
		for (int i = 1; i < h; i++)
			B[pos + h + i - 1] = max(0, B[pos + h + i - 1] - (h - i));

		int move = accumulate(B.begin(), B.end(), 0);
		if (minMove > move) minMove = move;
	}

	cout << minMove << endl;

	return 0;
}

int main()
{
	//clock_t start, end;
	//start = clock();

	yuki0077();

	//end = clock();
	//printf("%d msec.\n", end - start);

	return 0;
}