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문제

Aaron has a large supply of blocks and has challenged Andrew to build a structure out of them. All of the blocks are k × 1 × 1 for various values of k. The structure must be made up of n nonempty columns lined up in a sequence such that all blocks in column i have dimensions hi × 1 × 1, and have a 1 × 1 face that is parallel to the ground. Moreover, the structure must be a pyramid. A pyramid must contain an apex column such that for each column j to the left of the apex, the height of column j is no more than the height of column j + 1 and for each column k to the right of the apex, the height of column k is no more than the height of column k −1. For example, the left structure in Figure A.1 is not a pyramid since it does not have an apex column, while the right structure is a pyramid because the third column from the left is an apex column (as is the fourth column from the left).

Figure A.1: (left) An example that is not a pyramid. (right) An example of a pyramid. In both cases, n = 8 with blocks of size 6, 8, 4, 5, 6, 4, 2, 3 in the columns from left to right. This sequence is given in Sample Input 3.

Of course, just building a pyramid is easy, so Aaron has asked Andrew to find the pyramid with the smallest volume given a sequence of block sizes to use. Help Andrew by determining the smallest volume possible. You may assume that there is an unlimited supply of blocks of each size.

입력

The input starts with a line containing a single integer n (1 ≤ n ≤ 200 000), which is the length of the sequence.

The second line describes the blocks. This line contains n integers h1, h2, . . . , hn (1 ≤ hi ≤ 100 000), denoting that the blocks used in column i must be hi × 1 × 1.

출력

Display the smallest volume of a pyramid.

예제 입력 1

1
1337

예제 출력 1

1337

예제 입력 2

3
99 15 11

예제 출력 2

125

예제 입력 3

8
6 8 4 5 6 4 2 3

예제 출력 3

49