#include <stdio.h>
int main (void){
	int n,a,b;
	double c;
	while(scanf("%d",&n)!=EOF){
		c=0;
		b=0;
		while(n--){
			scanf("%d",&a);
			if(a>0){
				c=c+a*(1.0)/2;
			}
			else{
			c=c+a;
		}
		if(c<0){
			b++;
		}
		}
		printf("%d\n",b);
	}
	return 0;
	}