#include<stdio.h>
int main(){
	int i,n,a[10000],b,c;
	while(scanf("%d",&n)!=EOF){
		b=0;
		c=0;
		for(i=0;i<n;i++){
		scanf("%d",&a[i]);
		if(a[i]>0) a[i]=a[i]/2.0;
		b=b+a[i];
		if(b<0) c++;
		}
		printf("%d\n",c);
	}
}