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