#include<stdio.h>
int main(){
	int n;
	while(scanf("%d",&n)!=EOF){
		int sum=0;
		int k,ans=0;
		while(n--){
			scanf("%d",&k);
			if(k>0)
			sum+=k/2;
			else sum+=k;
		if(sum<0)
		ans++;
	}printf("%d\n",ans);
}}