#include<stdio.h>
#include<iostream>
#include<cmath>
using namespace std;
int main(){
	int n;
	while (scanf("%d",&n)!=EOF){
		double ans = 0;
		int anss = 0;
		while (n--){
			int a;
			scanf("%d", &a);
			if (a > 0)
				ans += a / 2.0;
			else
				ans += a;
			if (ans < 0)
				anss++;
		}
		printf("%d\n", anss);
	}
	return 0;
}