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Problem Statement

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 $i$ $(1 \leq i \leq N-1)$ is $A_i$. It can be shown that the final score of person $N$ is uniquely determined regardless of the sequence of games.

Input

The input consists of:

• A single integer $N$ $(2 \leq N \leq 100)$ — the number of people.
• A list of $N-1$ integers $A_1, A_2, \ldots, A_{N-1}$ $(-100 \leq A_i \leq 100)$ — the final scores of persons $1$ to $N-1$.

Output

Print the final score of person $N$.

Example

Input 1

4
1 2 -1

2

Explanation

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.

1. Persons $1$ and $2$ play, and person $1$ wins. The players now have $1, -1, 0, 0$ points.
2. Persons $1$ and $4$ play, and person $4$ wins. The players now have $0, -1, 0, 1$ points.
3. Persons $1$ and $2$ play, and person $1$ wins. The players now have $1, -2, 0, 1$ points.
4. Persons $2$ and $3$ play, and person $2$ wins. The players now have $1, -1, -1, 1$ points.
5. Persons $2$ and $4$ play, and person $4$ wins. The players now have $1, -2, -1, 2$ points.

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