#include<stdio.h>

void main(){
	int n,a,b,p;
	while(scanf("%d",&n)!=EOF){
		p=0;
		b=0;
		while(n--){
			scanf("%d",&a);
			if(a<0){
				if(a+b<0){
					b+=a;
					p++;
				}
				else
					b+=a;
			}
			else{
				if(b+a/2<0){
					b+=a/2;
					p++;
				}
				else
					b+=a/2;
			}
		}
		printf("%d\n",p);
	}
}