#include<stdio.h>
int main(){
	int t,a[1000];
	int i;
    while(scanf("%d",&t)!=EOF)
    {
    	int sum=0,sum1=0;
	for(i=0;i<t;i++){
		scanf("%d",&a[i]);
		if(a[i]>0)
	{
		a[i]=a[i]/2;
		sum=sum+a[i];
    }   else 
        sum=sum+a[i];
		if(sum<0)
		sum1=sum1+1;
	}
     	
        printf("%d\n",sum1);
}return 0;
}