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