#include<stdio.h>
int main (void){
	int n,i;
	int a,sum=0;
	while(scanf("%d",&n)!=EOF){
		int w=0;
		sum=0;
		for(i=1;i<=n;i++){
			scanf("%d",&a);
			a=(a>=0)?a/2:a;
			sum=sum+a;
			w=(sum<0)?++w:w;
		}
		printf("%d\n",w);
	}
	return 0;
}