#include<stdio.h>
int main(void){
	int n,a,i,t=0;
	double sum=0;
	while(scanf("%d",&n)!=EOF){
	for(i=0;i<n;i++){
		scanf("%d",&a);
		if(a>0)
		sum=sum+a/2.0;
		else
		sum=sum+a;
		if(sum<0)
		t=t+1;
	}
	printf("%d\n",t);
	t=0;
	sum=0;
	}
	return 0;
}