#include <stdio.h>
#include <math.h>
int main(){
	int n,step,sum=0,qzz=0;
	while(scanf("%d",&n)!=EOF){
		sum=0;
		qzz=0;
		getchar();
		while(n>0){
			scanf("%d",&step);
			if(step>0){
				step=step/2;
			}	
			sum=sum+step;
			if(sum<0){
				qzz+=1;
			}
			n--;
		}
		printf("%d\n",qzz);
	}
    return 0;
}