#include<stdio.h>
#include<math.h>
int main(){
	int T,i,m;
	double sum1,sum2,a;
	while(~scanf("%d",&T)){
		sum1=0;
		sum2=0;
		for(i=1;i<=T;i++){
			scanf("%lf",&a);
			if(a>0)
				sum1+=a/2.0;
			if(a<=0)
				sum1+=a;
			if(sum1<0)
				sum2+=1;
		}
		printf("%.0f\n",sum2);
	}
}