#include<stdio.h>
int main(){
	int count;
	int n;
	int m;
	double temp;
	while(scanf("%d",&n)!=EOF){
		count=0;temp=0;
		while(n--){
			scanf("%d",&m);
			if(m>0)
				temp+=(m/2.0);
			else
				temp+=m;
			if(temp<0)
			count++;

		}
		printf("%d\n",count);
		}
	return 0;
}