Description

There are $N$ people labeled $1$ to $N$, who have played several one-on-one games without draws. Initially, each person started with $0$ points. In each game, the winner's score increased by $1$ and the loser's score decreased by $1$ (scores can become negative). Determine the final score of person $N$ if the final score of person $i (1\le i\le N−1)$ is $A_i$. It can be shown that the final score of person $N$ is uniquely determined regardless of the sequence of games.

Constraints

$2\le N\le 100$

$−100\le A_i\le 100$

All input values are integers.

Format

Input

The input is given from Standard Input in the following format:

$N$

$A_1$ $A_2$ ... $A_{N-1}$

Output

One integer, the answer

Samples

4
1 -2 -1

2

Here is one possible sequence of games where the final scores of persons 1,2,3 are 1,−2,−1, respectively.

Initially, persons 1,2,3,4 have 0,0,0,0 points, respectively. Persons 1 and 2 play, and person 1 wins. The players now have 1,−1,0,0 point(s).

Persons 1 and 4 play, and person 4 wins. The players now have 0,−1,0,1 point(s).

Persons 1 and 2 play, and person 1 wins. The players now have 1,−2,0,1 point(s).

Persons 2 and 3 play, and person 2 wins. The players now have 1,−1,−1,1 point(s).

Persons 2 and 4 play, and person 4 wins. The players now have 1,−2,−1,2 point(s).

In this case, the final score of person 4 is 2. Other possible sequences of games exist, but the score of person 4 will always be 2 regardless of the progression.

3
0 0

0

6
10 20 30 40 50

-150

Limitation

1s, 1024KiB for each test case.