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