#include<cstdio>
#include<cstdlib>
#include<iostream>
#include<algorithm>
#include<cstring>
#include<string>
#include<cmath>
using namespace std;
int a,b, n,T,sum,cnt;
int main(){
	while(~scanf("%d",&n)){
		sum=0,cnt=0;
		for(int i=0;i<n;i++){
			scanf("%d",&a);
			if(a>0)
			sum+=a/2;
			else sum+=a;
			if(sum<0)
			cnt++;
		}
		printf("%d\n",cnt);
	}
	return 0;
}