#include<stdio.h>
#include<math.h>
int main(){
int n,i,m;
double l,k;
while(scanf("%d",&n)!=EOF){
	k=0;
	m=0;
	for(i=0;i<n;i++){
	scanf("%lf",&l);
	if(l>0)
		k=k+l/2;
	else 
		k=k+l;
	if(k<0)
		m++;
	}
	printf("%d\n",m);
}
return 0;
}