#include<stdio.h>
int main(){
	int n,s,x=0;
	double q;
	while(scanf("%d",&n)!=EOF){
		q=0.0;
		x=0;
		while(n--){
			scanf("%d",&s);
			if(s>0)
				q+=s*1.0/2;
			else
				q+=s;
			if(q<0)
				x+=1;
		}
		printf("%d\n",x);
	}
}