#include<stdio.h>
int main(void){
	int n;
	double a,sum,qzz;
	while(scanf("%d",&n)!=EOF){
	sum=0;qzz=0;
		while(n--){
			
			scanf("%lf",&a);
			if(a>0){
				sum=sum+a/2;
			}
			else{
				sum=sum+a;
			}
			if(sum<0)
			qzz++;
		}
		printf("%.0f\n",qzz);
	}
	return 0;
}