Problem Statement
The Interpol of your country has just started its journey. Initially, they don’t have any manpower. So, they started hiring new employees in groups.
Meanwhile, crimes keep occurring within the country. One employee of Interpol can investigate only one crime during his/her lifetime.
If there is no employee free (isn't busy with a crime) during the occurrence of a crime, it will go untreated.
Given the chronological order of crime occurrences and employee hirings, find the number of crimes that will go untreated.
Input
The first line of input will contain an integer n (1 ≤ n ≤ 105), 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 employees 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 that will go untreated.
Let's consider the example of sample input:
- 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 employee 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.
