#include<stdio.h>
int main(){
	int n,t,a[100010],i;
	float s;
	while(scanf("%d",&n)!=EOF){
		s=0;t=0;
		for(i=0;i<n;i++){
			scanf("%d",&a[i]);
		}
		for(i=0;i<n;i++){
			if(a[i]<0)
				s+=a[i];
			else
				s+=a[i]/2.0;
			if(s<0)
				t+=1;
		}
		printf("%d\n",t);
	}
	return 0;
}