Let's Play Billiards Already

Time limit1sMemory limit1024 MB

Summary

Given N rain flags, anger rises by 1 on rainy days and falls by 1 otherwise, starting from 0. Print the sum of the anger over all N days.

Level: Easy1 of 10
Topics: Simulation, Implementation
Solved: No attempts yet

Problem

Dongwoo wants to play billiards with Suho. However, Suho is an extreme homebody and refuses to leave the house.

Dongwoo: Hyung, please come out already

Suho: I'll go if it doesn't rain lol

Dongwoo checks the weather for the next $N$ days. On a rainy day, Dongwoo cannot play billiards with Suho, so his anger builds up. Dongwoo's current anger is $0$ . Each day, Dongwoo checks whether it rains. If it rains, his anger increases by $1$ . If it does not, his anger decreases by $1$ . His anger can become negative.

Find the sum of Dongwoo's anger from day $1$ to day $N$ , so that he can avoid getting sick from bottled-up anger.

Input

The first line contains an integer $N$ . $(1 \le N \le 200\,000)$

The second line contains the weather for the $N$ days, separated by spaces. A rainy day is $1$ , and a day without rain is $0$ .

Output

Print the sum of Dongwoo's anger from day $1$ to day $N$ .

Hint

The sum can overflow 32-bit integers. Use the following types:

C, C++: long long
Java: long

Examples2

Example 1
Input
```
5
0 0 0 0 0
```
Expected output
```
-15
```
Example 2
Input
```
6
1 1 0 0 1 0
```
Expected output
```
5
```