#include<iostream>
using namespace std;
int main(){
int n,a[1000];
double sum,all,k;
while(scanf("%d",&n)!=EOF){
	sum=all=0;
for(int i=0;i<n;i++){
	scanf("%d",&a[i]);
}
for(int i=0;i<n;i++){
	if(a[i]>0){
		k=a[i]/2.0;
	}
	else k=a[i];
	sum+=k;
	if(sum<0){
		all++;
	}
}
	cout<<all<<endl;

}

}