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