#include<stdio.h>
int main(){
	int sum1,sum2,t,i;
	int a[100001];
	while(scanf("%d",&t)!=EOF){
		sum1=sum2=0;
		for(i=0;i<t;i++){
			scanf("%d",&a[i]);
			if(a[i]>0)
				sum1+=a[i]/2;
			else
				sum1+=a[i];
			if(sum1<0)
				sum2+=1;
		}
		printf("%d\n",sum2);
	}
}