Virtual contest is a way to take part in past contest, as close as possible to participation on time. It is supported only ACM-ICPC mode for virtual contests.
If you've seen these problems, a virtual contest is not for you - solve these problems in the archive.
If you just want to solve some problem from a contest, a virtual contest is not for you - solve this problem in the archive.
Never use someone else's code, read the tutorials or communicate with other person during a virtual contest.

No tag edit access

A. Police Recruits

time limit per test

1 secondmemory limit per test

256 megabytesinput

standard inputoutput

standard outputThe police department of your city has just started its journey. Initially, they don’t have any manpower. So, they started hiring new recruits in groups.

Meanwhile, crimes keeps occurring within the city. One member of the police force can investigate only one crime during his/her lifetime.

If there is no police officer free (isn't busy with crime) during the occurrence of a crime, it will go untreated.

Given the chronological order of crime occurrences and recruit hirings, find the number of crimes which will go untreated.

Input

The first line of input will contain an integer *n* (1 ≤ *n* ≤ 10^{5}), the number of events. The next line will contain *n* space-separated integers.

If the integer is -1 then it means a crime has occurred. Otherwise, the integer will be positive, the number of officers recruited together at that time. No more than 10 officers will be recruited at a time.

Output

Print a single integer, the number of crimes which will go untreated.

Examples

Input

3

-1 -1 1

Output

2

Input

8

1 -1 1 -1 -1 1 1 1

Output

1

Input

11

-1 -1 2 -1 -1 -1 -1 -1 -1 -1 -1

Output

8

Note

Lets consider the second example:

- Firstly one person is hired.
- Then crime appears, the last hired person will investigate this crime.
- One more person is hired.
- One more crime appears, the last hired person will investigate this crime.
- Crime appears. There is no free policeman at the time, so this crime will go untreated.
- One more person is hired.
- One more person is hired.
- One more person is hired.

The answer is one, as one crime (on step 5) will go untreated.

Codeforces (c) Copyright 2010-2017 Mike Mirzayanov

The only programming contests Web 2.0 platform

Server time: Jul/24/2017 03:41:47 (c4).

Desktop version, switch to mobile version.

User lists

Name |
---|