#include<stdio.h>
#include<stdlib.h>
#define SIZE 10000
int main(){
	int n,a,x,qiu;
	while(scanf("%d",&n)!=EOF){
		qiu=0;
		x=0;
		while(n--){
			scanf("%d",&a);
			if(a>=0)
			a=a/2;
			x=x+a;
			if(x<0)
			qiu++;
		}
		printf("%d\n",qiu);
	}
	return 0;
}