Contest Duration: ~ (local time) (100 minutes) Back to Home
B - Iron Bar Cutting /

Time Limit: 2 sec / Memory Limit: 1024 MB

### 問題文

DISCO 社の高橋君の前に，1 本の鉄の棒が置かれています．
この棒は，N-1 個の切れ目によって N 個の区間に分かれています．左から i 個目の区間の長さは A_i ミリメートルです．

そこで，彼は棒を切る前に，以下の操作を何回か行うことにしました．

• 棒の区間のうち 1 つを選び，膨張させ，長さを 1 ミリメートル増やす．この操作を 1 回行うのに 1 円かかる．
• 棒の区間のうち長さが 2 ミリメートル以上のもの 1 つを選び，収縮させ，長さを 1 ミリメートル減らす．この操作を 1 回行うのに 1 円かかる．

### 制約

• 2 \leq N \leq 200000
• 1 \leq A_i \leq 2020202020
• N, A_i は整数

### 入力

N
A_1 A_2 A_3 ... A_N


### 入力例 1

3
2 4 3


### 出力例 1

3


• 左から 2 番目の区間を収縮させる．各区間の長さは [2, 3, 3] となる．
• 左から 1 番目の区間を収縮させる．各区間の長さは [1, 3, 3] となる．
• 左から 2 番目の区間を収縮させる．各区間の長さは [1, 2, 3] となる．左から 2 個目の切れ目で棒を切ると，長さ 3 の棒が 2 本できる．

### 入力例 2

12
100 104 102 105 103 103 101 105 104 102 104 101


### 出力例 2

0


Score: 200 points

### Problem Statement

Takahashi, who works at DISCO, is standing before an iron bar. The bar has N-1 notches, which divide the bar into N sections. The i-th section from the left has a length of A_i millimeters.

Takahashi wanted to choose a notch and cut the bar at that point into two parts with the same length. However, this may not be possible as is, so he will do the following operations some number of times before he does the cut:

• Choose one section and expand it, increasing its length by 1 millimeter. Doing this operation once costs 1 yen (the currency of Japan).
• Choose one section of length at least 2 millimeters and shrink it, decreasing its length by 1 millimeter. Doing this operation once costs 1 yen.

Find the minimum amount of money needed before cutting the bar into two parts with the same length.

### Constraints

• 2 \leq N \leq 200000
• 1 \leq A_i \leq 2020202020
• All values in input are integers.

### Input

Input is given from Standard Input in the following format:

N
A_1 A_2 A_3 ... A_N


### Output

Print an integer representing the minimum amount of money needed before cutting the bar into two parts with the same length.

### Sample Input 1

3
2 4 3


### Sample Output 1

3


The initial lengths of the sections are [2, 4, 3] (in millimeters). Takahashi can cut the bar equally after doing the following operations for 3 yen:

• Shrink the second section from the left. The lengths of the sections are now [2, 3, 3].
• Shrink the first section from the left. The lengths of the sections are now [1, 3, 3].
• Shrink the second section from the left. The lengths of the sections are now [1, 2, 3], and we can cut the bar at the second notch from the left into two parts of length 3 each.

### Sample Input 2

12
100 104 102 105 103 103 101 105 104 102 104 101


### Sample Output 2

0