#include<stdio.h>
int main(){
	int n,x,y=0,z=0;
	while(scanf("%d",&n)!=EOF){
		while(n--){
			scanf("%d",&x);
			if(x>0)
			y+=x/2;
			else
			y+=x;
			if(y<0)
			z+=1;
			else
			z+=0;}
			printf("%d\n",z);
			y=0;
			z=0;
		}
	return 0;
}