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