#include<stdio.h>
int main(){
int n,i,c;
double b;
int a[1000];
while(scanf("%d",&n)!=EOF){
	b=0;
	c=0;
	for(i=0;i<n;i++){
		scanf("%d",&a[i]);
		if(a[i]>0)
			b+=(a[i]/2.0);
		else
			b+=a[i];
		if(b<0)
			c+=1;}
	printf("%d\n",c);}
}