#include<stdio.h>
int main(){
	int x,n,total;
	double i,y;
	long long m;
	while(scanf("%d",&n)!=EOF){
		total=0;
		y=0;
		while(n--){
		scanf("%d",&x);
		if(x>0) {
		i=x*1.0/2;
	}else{
		i=x;
	}
		 
		y+=i;
		if(y<0) total++;
	}
		printf("%d\n",total);
	}
	return 0;
}