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