#include<stdio.h>
#include<math.h>
#include<string.h>
int main(){
	int n;
	while(scanf("%d",&n)!=EOF){
		int qzz=0;
		double sum=0;
		int i,j,a[10000];
		for(i=0;i<n;i++){
			scanf("%d",&a[i]);
		}
		for(j=0;j<n;j++){
			if(a[j]>0)
				sum+=1.0*a[j]/2;
			else
				sum+=a[j];
			if(sum<0)
				qzz++;
		}
		printf("%d\n",qzz);
	}
	return 0;
}