#include<stdio.h>
int main(void){
	int a,b,c,d;
	while(scanf("%d",&a)!=EOF){
		c=0;d=0;
		while(a--){
        scanf("%d",&b);
		if(b>0)
		c=c+(0.5)*b;
		else c=c+b;
		if(c<0)d++;}printf("%d\n",d);}
	return 0;}