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