using namespace std;
#include<string>
#include <iostream>

int main(){

	int n,a[100];
	cin >> n;

	for (int i = 0; i < n; i++) {
		cin >> a[i];
		
	}
	int sum = 0;
	int count = 0;
	for (int i = 0; i < n; i++) {
		
		
		if (a[i] == 0)
			continue;
		
			sum =sum+a[i];
			if(sum<0)
				count = count + abs(sum);
		    
	}
	cout << count;






}