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