#include<stdio.h>
#include<math.h>
#include<string.h>
#include<stdlib.h>
int main()
{
int n;
while(scanf("%d",&n)!=EOF){
	int a[n],x=0,l=0;
	for(int i=0;i<n;i++){
		scanf("%d",&a[i]);
		if(a[i]<0)
		x+=a[i];
		else
		x+=a[i]/2.0;
		if(x<0)
		l++;
	}
	printf("%d\n",l);
}
	return 0;
}