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