#include<stdio.h>
#include<math.h>
#include<string.h>
int main(){
	int n,i;
	int a[1000];
	while(scanf("%d",&n)!=EOF){
		double luckynum=0;
		int qzz=0;
		for(i=0;i<n;i++){
			scanf("%d",&a[i]);
			if(a[i]>0){
				luckynum+=1.0*a[i]/2;
			}
			else
				luckynum+=a[i];
			if(luckynum<0)
				qzz++;
		}
		printf("%d\n",qzz);
	}
	return 0;
}