#include<stdio.h>
int main(){
	int n,i;
	int s=0;
	int m=0;
	int a[100000];
while(scanf("%d",&n)!=EOF){
for(i=0;i<=n-1;i++){
scanf("%d",&a[i]);
if(a[i]>0){a[i]=a[i]/2;}
s=s+a[i];
if(s<0){m=m+1;}
}
printf("%d\n",m);
s=0;
m=0;
}
return 0;
}