#include<stdio.h>
int main(){
	int a,c,d,i;
	int b[10000],e[10000];
	while(scanf("%d",&a)!=EOF){
		c=0;
		d=0;
	for(i=0;i<a;i++){
		scanf("%d",&b[i]);
		if(b[i]>0)
			e[i]=b[i]/2;
		else
			e[i]=b[i];
		c+=e[i];
		if(c<0)
			d+=1;
	}
	printf("%d\n",d);
	}
	return 0;
}