Get Minimum Time

Carry the boxes of each floor to the top floor with separate round trips from that floor; each box requires one round trip plus 1 minute of loading and unloading.

The standard input/output format and supplementary bounds of this site are as stated in this problem.

输入格式

The first line contains n (1≤n≤10^5); the second line contains n non-negative integers boxes[i] (≤10^9), where index i corresponds to floor i and the top floor is n.

输出格式

Output the minimum total number of minutes (the integer may exceed 32 bits).

样例 1

输入：

4
2 1 0 1

输出：

28

样例 2

输入：

1
0

输出：

0

样例 3

输入：

3
0 0 2

输出：

6