#include<stdlib.h>
#include<stdio.h>
#include<math.h>
#include<string.h>
int main(){
	int i,x,n,a[1000];
	while(scanf("%d",&n)!=EOF){
		int q=0,m=0;
	    for(i=0;i<n;++i){
		    scanf("%d",&a[i]);
			if(a[i]>=0)
				a[i]=a[i]/2;
			m+=a[i];
			if(m<0)
				q+=1;
		}
		printf("%d\n",q);
	}
}