import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] arr = new int[1000];
        int total = 0;
        for (int i = 0; i < n; i++) {
            arr[i] = sc.nextInt();
            total += arr[i];
        }
        int min = Integer.MAX_VALUE;
        for (int i = 1; ; i += 2) {
            int height = i / 2 + 1;
            if (height * height > total) {
                break;
            }
            int length = height * 2 - 1;
            int count = 0;
            int size = 1;
            int idx = 1;
            while (idx < arr.length) {
                if (arr[idx - 1] == 0 && size == 0) {
                    break;
                }
                count += Math.max(arr[idx - 1] - size, 0);
                if (idx >= height) {
                    size--;
                    if (size < 0) {
                        size = 0;
                    }
                } else {
                    size++;
                }
                idx++;
            }
            min = Math.min(min, count);
        }
        System.out.println(min);
    }
}