#include<stdio.h>
int main(void){
int n,a[1000],c,d,i;
double b;
while(scanf("%d",&n)!=EOF){
	b=0,d=0;
	for(i=1;i<=n;i++){
		scanf("%d",&a[i]);
	}
	for(i=1;i<=n;i++){
		if(a[i]>0)
			b=b+a[i]/2.0;
		else
			b=b+a[i];
		if(b<0)
			d=d+1;
	}
	printf("%d\n",d);
}


}