#include<stdio.h>
#include<string.h>
#include<math.h>
int main()
{
	int n,a,ans;
	double sum=0;
	while(scanf("%d",&n)!=EOF){
		sum=0,ans=0;
		for(int i=0;i<n;i++){
			
			scanf("%d",&a);
			if(a>0)
				sum+=a/2;
			else
				sum+=a;
			if(sum<0)
				ans++;
		}
		printf("%d\n",ans);
	}
	return 0;
}