#include<stdio.h>
#include<math.h>
#include<string.h>
int main(){
	int n,a,i,sum,b;
	while(scanf("%d",&n)!=EOF){
		a=0;
		sum=0;
		for(i=0;i<n;i++){
			scanf("%d",&b);
			if(b>0){
			   b/=2;
			}
			a+=b;
			if(a<0){
				sum++;
			}
		}
		printf("%d\n",sum);
	}
	
	return 0;
}