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