#include<stdio.h>
int main(void){
	int n,a[10000];
	while(scanf("%d",&n)!=EOF){
		int i,h,m=0,sum=0;
		for(i=0;i<n;i++){
			scanf("%d",&a[i]);
			if(a[i]>0)
				h=a[i]*0.5;
			else
				h=a[i];
			m=m+h;
			if(m<0)
				sum=sum+1;
		}
		printf("%d\n",sum);
	}
	return 0;
}