#include<stdio.h>
#include<math.h>
int main(){
int n;

while(scanf("%d",&n)!=EOF){
	int a[n];
	int k=0,i,m=0;
	for(i=0;i<n;i++){
		scanf("%d",&a[i]);
		if(a[i]>0)
		k+=a[i]/2;
		else
		k+=a[i];
		if(k<0)
		m+=1;
		}
	printf("%d\n",m);
}
return 0;
}