#include<stdio.h>
#include<math.h>
int main(){
	int n,i,a,q;
	double x;
	while(scanf("%d",&n)!=EOF){
		x=0;
		q=0;
		while(n--){
		scanf("%d",&a);
		if(a>=0)
			x=x+a/2.0;
		else
			x=x+a;
		if(x<0)
			q=q+1;
		}
		printf("%d\n",q);
	}
}