#include<stdio.h>
#include<string.h>
#include<algorithm>
#include<iostream>
#include<stdlib.h>
#include<math.h>
#include<map>
#include<set>
#include<queue>
#include<vector>
using namespace std;
int T,t,y,m;
char s[1100];
double p,q;
int main()
{
	long long n,x,ans;
	while(~scanf("%lld",&n)){
		double sum=0;ans=0;
		for(long long i=1;i<=n;i++){
			scanf("%lld",&x);
			if(x>0){
				sum+=x/2.0;
			}else sum+=x;
			if(sum<0) ans+=1;
		}
		printf("%lld\n",ans);
	}
	
}