#include<stdio.h>
int main(){
	int t,i,a[1000];
	while(scanf("%d",&t)!=EOF){
		int sum=0,s=0;
		for(i=0;i<t;++i){
			scanf("%d",&a[i]);
		}
		for(i=0;i<t;++i){
			if(a[i]<0) sum+=a[i];
			else sum=sum+a[i]/2;
			if(sum<0) s++;
		}
		printf("%d\n",s);
	}
}