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