#include<stdio.h>
int main(){
	int n,a[100000],s,last,i;
	while(scanf("%d",&n)!=EOF){
		s=last=0;
		for(i=0;i<n;++i){
			scanf("%d",&a[i]);
			if(a[i]>0){
				s=s+a[i]/2.0;
				if(s<0)
				    last++;
			}
			else{
			    s=s+a[i];
			    if(s<0)
				    last++;}
		}
		printf("%d\n",last);
	}
	return 0;
}