#include<iostream>
int main()
{
	int T;
	while(scanf("%d",&T)!=EOF){
		int a;
		double sum=0;
		int sum1=0;
		while(T--){
			scanf("%d",&a);
			if(a>0)
			sum+=1.0*a/2;
			else
			sum+=a;
			if(sum<0)
			sum1++;
		}
		printf("%d\n",sum1);
	}
	return 0;
}