#include<bits/stdc++.h>
using namespace std;
int main(){
	int n,i,a,cnt,sum;
	int s[1000];
	while(scanf("%d",&n)!=EOF){
		cnt = 0;sum = 0; 
		for(i=1;i<=n;i++){
			scanf("%d",&s[i]);
		}
		for(i=1;i<=n;i++){
			if(s[i]>0){
				sum+=s[i]/2;
			}
			else{
				sum+=s[i];
			}
			if(sum<0){
				cnt++;
			}
		}
		printf("%d\n",cnt);
	}
}