#include<stdio.h>
#include<stdlib.h>
#include<math.h>
#include<string.h>
int main(){
	int n,a[10000],i,num=0;
	double d=0;
	while(scanf("%d",&n)!=EOF){
		d=0;
		num=0;
		memset(a,0,sizeof a);
		for(i=0;i<n;i++){
			scanf("%d",&a[i]);
			if(a[i]>=0)
				d=d+1.0*a[i]/2;
			else
				d=d+a[i];
			if(d<0)
				num=num+1;
		}
		printf("%d\n",num);
	}
}