#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;
}